Cannabis Harms Glossary

This glossary provides an overview of potential harms associated with cannabis use, organized alphabetically for easy reference. Each entry includes summaries of key research findings, expanded details where available, and references to medical literature. This resource is inspired by and draws heavily from the IASIC Library, focusing on evidence-based information from published studies. Additional modern information (2024–2025) has been incorporated based on recent studies to highlight ongoing risks and harms.

Addiction / Cannabis Use Disorder

Among people age 12 or older, the percentage with a past year marijuana use disorder was 1.8% in 2002 (or 4.3 million people) and 2019 (or 4.8 million people) but showed declines in some years. Key Substance Use and Mental Health Indicators in the United States: Results from the 2019 National Survey on Drug Use and Health. SAMHSA. Published September 2020.

9% of those who experiment with marijuana will become addicted. - 17% of teenagers who experiment with marijuana become addicted. - 25-50% of daily users become addicted. Bell CC. DSM-IV: Diagnostic and Statistical Manual of Mental Disorders. JAMA. 1994;272(10):828-29.

19.5% of lifetime users met criteria for DSM 5 Cannabis Use Disorder of whom 23% have severe symptoms and of those 48% were not functioning (not working). Hasin DS. US Epidemiology of Cannabis Use and Associated Problems. Neuropsychopharmacology. 2018;43(1):195-212 .

  • This study included 24,900 surveys from the 2015 -2015 National Survey on Drug Use and Health. Mother or Father use of marijuana was associated with higher risk of substance use in adolescents and young adults living in the same household. This included increased use of marijuana, tobacco, alcohol and opioid misuse in offspring of parents who used marijuana. Madras, BK. Et al. Associations of Parental Marijuana Use With Offspring Marijuana, Tobacco, and Alcohol Use and Opioid Misuse. JAMA. Addiction. JAMA, 2019.
  • This study is published by the National Institute of Health, NIH and the director of NIDA, the National Institute of Drug Abuse. Data from the 2018 National Survey on Drug Use and Health, NSDUH confirmed previous studies showing that the younger the age of initiation of drugs, the faster the transition to developing addiction (substance use disorder). The prevalence of cannabis use disorder (marijuana addiction) for youth age 12 - 17 was 10.7% if using less than one year or 20.1% if using more than 3 years. The prevalence of cannabis use disorder was higher than alcohol use disorder in this age group. Volkow ND, Han B, Einstein EB, Compton WM. Prevalence of Substance Use Disorders by Time Since First Substance Use Among Young People in the US. JAMA Pediatr. Published online March 29, 2021. doi:10.1001/jam apediatrics.2020.6981

808 5 th graders from Seattle public schools serving high crime areas were followed until age 33. Non marijuana users reported fewer symptoms of alcohol use disorder, nicotine dependence, and general anxiety disorder. Persistent, regular marijuana use in young adulthood correlated with more symptoms of cannabis use disorder, alcohol use disorder, and nicotine dependence at age 33. Guttmannova, et al. The association between regular marijuana use and adult mental health outcomes. Drug Alcohol Depend. 2017;179:109-116. doi: 10.1016/j.drugalcdep.2017.06.016.

A 2025 study in JAMA Network Open found that brain function outcomes of recent and lifetime cannabis use show impacts on cognition, with evidence from a 2024 study suggesting brain analysis should consider features like function and connectivity. Surveys indicate older adults use cannabis for pain, but addiction risks persist, with 20.6 million people estimated to have CUD in 2024. Early teen use significantly increases risks for serious health problems in adulthood.

Allergies

  • Allergic disease associated with C sativa exposure and use has been reported with increased frequency, including anaphylaxis. Although relatively uncommon, allergies have been reported with increased frequency. Ocampo TL and Rans TS. Cannabis sativa: the unconventional “weed” allergen. Ann Allergy Asthma Immunol. 2015;114(3):187-192. doi: 10.1016/j.anai.2015.01.004

Allergists report cannabis allergy is increasingly common, causing rhinitis, conjunctivitis, hives, asthma, angioedema, and classical anaphylaxis (Psychology Today, 2025). A 2025 study investigated the associative impact of recreational cannabis use on sinonasal symptoms in patients with chronic rhinosinusitis, allergic rhinitis, or chronic rhinitis. The growing use of cannabis raises concerns about its cutaneous adverse effects, including allergic reactions.

Alzheimer’s Disease (Note: Limited direct information available in the source material. Based on related neurocognitive effects, cannabis use may exacerbate cognitive decline, but specific studies on Alzheimer's are not detailed. Refer to Neurocognitive Effects for broader insights.)

Heavy, long-term marijuana use is linked to accelerated cognitive decline and an elevated risk of dementia, including Alzheimer’s disease, through multiple harmful pathways. THC promotes brain inflammation, oxidative stress, and amyloid-beta plaque accumulation—hallmarks of Alzheimer’s pathology—while disrupting cerebral blood flow and tau protein regulation .

Amotivational Syndrome

  • The research team found that only marijuana (but not alcohol or tobacco) intake significantly and longitudinally prompted lower initiative and persistence and provides partial support for the marijuana amotivational syndrome. Lac A and Luk JW. Testing the Amotivational Syndrome: Marijuana Use Longitudinally Predicts Lower Self-Efficacy Even After Controlling for Demographics, Personality, and Alcohol and Cigarette Use. Prevention Science. 2018 Feb;19(2):117–126

Heavy, long-term marijuana use is associated with amotivational syndrome, characterized by diminished initiative, persistence, and goal-directed behavior, particularly among adolescents and young adults whose developing brains are highly susceptible to THC-induced disruptions in the brain's reward and dopamine systems. Chronic exposure blunts dopamine release and reward sensitivity in the nucleus accumbens and prefrontal cortex, leading to apathy, reduced self-efficacy, and lower effort in tasks requiring sustained motivation, even after accounting for confounders like depression, personality traits, and other substance use . Overall, while not all users experience severe apathy, the syndrome underscores marijuana's role as a risk factor for behavioral disengagement, especially in youth, with no robust protective effects observed in recent legalization-era data.

Anesthesia / Surgery / Pain Medications

Bispectral Index, BIS, brain wave monitoring, was increased for people using high dose cannabis. Ibera C, Shalom B, Saifi F, Shruder J, Davidson E. Effects of Cannabis Extract Premedication on Anesthestic Depth. Harefuah. 2018 Mar;157(3):162-166. Hebrew. PMID: 29582946. - A study of 118 patients in Colorado with isolated tibia fractures requiring surgery showed that preoperative cannabis use leads to increased tolerance to Sevoflurane. Holmen IC, Beach JP, Kaizer AM, Gumidyala R. The association between preoperative cannabis use and intraoperative inhaled anesthetic consumption: A retrospective study. J Clin Anesth. 2020 Dec. - A study of 4,186,622 patients that required elective surgery showed a higher incidence of heart attack in people with cannabis use disorder, Odds Ration 2.88. Akash Goel, Brandon McGuinness, Naheed K. Jivraj, Duminda N. Wijeysundera, Murray A. Mittleman, Brian T. Bateman, Hance Clarke, Lakshmi P. Kotra, Karim S. Ladha; Cannabis Use Disorder and Perioperative Outcomes in Major Elective Surgeries: A Retrospective Cohort Analysis Anesthesiology 2020; 132:625–635 doi: https://doi.org/10.1097/ALN.0000000000003067 * A study of 319 patients in London, Ontario showed daily cannabis users required higher dose of propofol. Imasogle N, Rose RV, Wilson A: High quantities: Efaluating the association between cannabis use and propofol anesthesia during endoscopy. PLOS One. March 2021. - A study of 318 patients in Colorado that required endoscopy showed that cannabis users required 14% more fentanyl, 18.6% more midazolam, and 220.5% more propofol. Twardowski MA, Link MM, Twardowski NM. Effects of Cannabis Use on Sedation Requirements for Endoscopic Procedures. J Am Osteopath Assoc. 2019 Apr 15. doi: 10.7556/jaoa.2019.052. Epub ahead of print. PMID: 30985870. - A comprehensive review of pharmacological and anesthetic considerations showed that combination of cannabinoids and anesthetic agents can have serious consequences including severe vascular consequences, bronchial hyperactivity, hypotension, and platelet aggregation. Echeverria-Villalobos M, Todeschini AB, Stoicea N, Fiorda-Diaz J, Weaver T, Bergese SD. Perioperative care of cannabis users: A comprehensive review of pharmacological and anesthetic considerations. J Clin Anesth. 2019 Nov;57:41-49. doi: 10.1016/j.jclinan

  • This study reviewed 12,422 hospitalizations after major elective non cardiac surgery and found increased complications in patients with a cannabis use disorder (7.73%) compared to those who do not use cannabis (6.56%). Potnuru PP, Jonna S, Williams GW. Cannabis Use Disorder and Perioperative Complications. JAMA Surg. Published online July 05, 2023. doi:10.1001/jamasurg.2023.2403

The American Society for Regional Anesthesia, ASRA published a consensus guidelines for managing perioperative patients on cannabis or cannabinoids. The recommendations include: - Universal screening of cannabinoids before surgery - Counseling patients with frequent, heavy cannabis use on the negative effects of post operative pain control - Postposing elective surgery on patients who are impaired or intoxicated on cannabis ASRA Consensus Guidelines on the Management of the Perioperative Patient on Cannabis or Cannabinoids. Jan 2023

Perioperative Repercussions of Cannabis Use—Implications for GI Surgery (PMC, 2025) notes cannabis smoking may have a greater impact on propofol requirements due to airway irritability. Cannabis Versus Opioids for Pain in StatPearls (2023, updated 2025) discusses harms in pain management. Cannabis blunts back pain in 2 new studies (NPR, 2025) but with risks. Cannabis Use Complicates Anesthesia, Duke Review Warns (2025) urges routine cannabis screening. Effect of Preoperative Cannabis Use on Postoperative Pain (2025) found complications.

Anxiety

Prospective study showing adolescent users have nearly triple the odds of an adult anxiety disorder. Although a previous systematic review examining adulthood anxiety among adolescent cannabis users reporting conflicting data on this association. (Moore et al. Cannabis use and the risk of psychotic or affective mental health outcomes: a systematic review. Degenhardt et al. The persistence of the association between adolescent cannabis use and common mental health disorder into young adulthood. Addiction. 2013 Jan;108(1):124-33. doi: 10.1111/j.1360-0443.2012.04015.

Research on Depression, Anxiety, PTSD (Psychiatry Podcast, 2025) notes cannabis has not been found to improve anxiety disorders. Frequency of cannabis use and symptoms of anxiety and depression (2025) found frequent use associated with elevated anxiety symptoms. New Research: Cannabis for Anxiety Relief in 2025 (Veriheal, 2025) shows mixed results, with harms like increased dependence.

Autism

  • 3,080 young adult Australian twins were used to assess ADHD symptoms, autistic traits, substance use, and substance use disorders. Great ADHD symptoms and autistic traits scores were associated with elevated levels of cannabis use and cannabis use disorder. DeAkwis D, et al. ADHD Symptoms, Autistic Traits, and Substance Use and Misuse in Adult Australian Twins. Journal of Studies on Alcohol and Drugs, March 2014.

  • This review examined the epidemiology of cannabis use among children and adolescents, including those with developmental and behavioral diagnosis. It then outlined the well-recognized neurocognitive changes shown to occur in adolescents who use cannabis regularly, highlighting the unique susceptibility of the developing adolescent brain and describing the role of the endocannabinoid system in normal neurodevelopment. They conclude that cannabis cannot be safely recommended in the treatment of developmental or behavioral disorders such as ADHD and autism spectrum disorder at this time. Hadland SE, et al. Medical Marijuana: Review of he Science and Implication for Developmental Behavioral Pediatric Practice. J Dev Behav Pediatr. 2015.

  • Preconception cannabis use in males can have effect on subsequent generations because cannabis use is associated with widespread DNA changes in human sperm. Discs-Large Associated Protein 2 (DLGAP2), involved in synapse organization, neuronal signaling, and strongly implicated in autism, exhibited significant hypomethylation sites in human sperm. Scrott R, et al. Cannabis use is associated with potentially heritable widespread changes in autism candidate gene GLGAP2 DNA methylation in sperm. Epigenetics. 2019.

  • Datasets from US Department of Education Individuals with Disabilities Act (IDEA), National Survey of Drug Use and Health, and CDC’s Autism and Developmental Disabilities Monitoring (ADDM) Network were investigated. Data on legal status was derived from SAMHSA. Autism Spectrum Disease (ASD) was found to be the most common form of cannabis-associated clinical tetralogy. The authors showed that medical, decriminalized and legal cannabis regies are associated with higher rates of ASD than illegal ones. Reece AS and Hulse GK. Effect of Cannabis Legalization on US Autism Incidence and Medium Term Projections. Clinical Pediatrics. Vol 4, Iss 2, No:154 Reese SA and Hulse GK. Epidemiological Association of Various Substances and Multiple Cannabinoids with Autism in the USA. Clinical Pediatrics., Vol 4, Issue2, No: 155. Reese SA and Hulse GK. Epidemiological Association of Various Substances and Multiple Cannabinoids with Autism in the USA. Clinical Pediatrics., Vol 4, Issue2, No: 155.

  • Studies on medical cannabis (mostly CBD-rich) for autistic children reveal notable negative effects. A 2022 systematic review found adverse events in up to 27% of participants, including agitation, aggression, and rare psychotic episodes requiring discontinuation. Aran et al. (2019) reported side effects in 32% of 60 children, such as sleep disturbances (14%), irritability (9%), and appetite loss (9%), with one case of transient psychosis. Barchel et al. (2019) noted somnolence (21%) and appetite changes (17%) in 25% of cases, plus worsening anxiety in 23.5%. A 2025 meta-analysis confirmed dizziness, insomnia, and weight gain in nearly 10%, with long-term risks like liver issues unknown. Reviews consistently highlight behavioral worsening, psychosis risk (especially with THC), and overlap with ASD symptoms, urging caution and more rigorous trials due to clear harms in vulnerable kids.

Cancer

This study included 116,076 individuals with cannabis use disorder (CUD) and 3,985,286 individuals without CUD. People with CUD had a 3.49 higher risk of any head and neck cancer The risk for chronic cannabis users for oral cancer was 2.51, oropharyngeal cancer was 4.9 and laryngeal cancer was 8.39. Gallagher TJ, et al. Cannabis Use and Head and Neck Cancer. JAMA Otolaryngol Head and Neck Surg. Aug 2024.

  • A study of 369 men ages 18 – 44 between 1999-2006 showed that men with testicular germ cell tumors were more likely than controls to be current marijuana smokers. Nonseminoma and mixed histology tumors had a higher odd ratio of 2.3 for current marijuana users. Daling JR et al. Association of marijuana use and the incidence of testicular germ cell tumors . Cancer. 2009;115(6):1215-1223. doi: 10.1002/cncr.24159 * Ever use of marijuana had a 2-fold increased risk of testicular germ cell tumor compared to never users in a study of 163 patients in LA County between 1986 – 1991. Nonseminoma and mixed histology tumors were associated with a higher 2.42 odd ratio. Lackson JC, Carroll JD, Tuazon E, Castelao EJ, Bernstein L, Cortessis VK. Population-based case control study of recreational drug use and testis cancer risk confirms an association between marijuana use and nonseminoma risk. Cancer. 2012;118(21):5374-83. * Patients with testicular germ cell tumors have increased in the United States, 187 patients diagnosed with this cancer between 1990-1996 were more likely to be frequent marijuana users (daily or greater) than controls (odd ratio 2.2). Nonseminoma cancers had a higher odd ratio of 3.1. Traber B, Sigurdson AJ, Sweeney AM, Strom SS, McGlynn KA. Marijuana use and testicular germ cell tumors. Cancer. 2011;117(4):848-53. doi: 10.1002/cncr.25499.
  • The CDC database on cancer surveillance showed that total pediatric cancer incidence rates increased 49% between 1975 and 2015. Cannabis use was showed to be spatiotemporally and casually related to the rise in pediatric cancers. The extensive analysis proved that THC and cannabigerol were a cause of pediatric cancers, meeting the criteria of causation rather than association. Reece, A.S., Hulse, G.K. A geospatiotemporal and causal inference epidemiological exploration of substance and cannabinoid exposure as drivers of rising US pediatric cancer rates. BMC Cancer 21, 197 (2021
  • ALL, Acute Lymphoid Leukemia is the most common childhood cancer who incidence rose 93.51% in 20 years. The researchers used data from the CDC, the National Cancer Institute and the National Survey on Drug Use and Health showing that cannabis consumption is associated with ALL and satisfied the criteria for causality. Reece, A.S., Hulse, G.K. Cannabinoid exposure as a major driver of pediatric acute lymphoid Leukaemia rates across the USA: combined geospatial, multiple imputation and causal inference study. BMC Cancer 21, 984 (2021).
  • Heavy, long-term marijuana use, particularly through smoking, is associated with an increased risk of several cancers, including head and neck, lung, and testicular germ cell tumors (TGCT), due to the presence of carcinogens like polycyclic aromatic hydrocarbons (PAHs) and tar in cannabis smoke, which mirror those in tobacco but at higher concentrations per inhalation. Cannabis use disorder (CUD) elevates the relative risk of any head and neck cancer (HNC) by 3.49-fold, with site-specific risks including oral cancer (RR 2.51), oropharyngeal cancer (RR 4.90), and laryngeal cancer (RR 8.39), based on a 2024 cohort analysis of over 231,000 U.S. adults, independent of tobacco or alcohol use

Cannabis Hyperemesis Syndrome (Scromiting)

  • Vomiting Syndrome Discovered in Some Long-Term Marijuana Users: Researchers The condition has become so common, ER staff have coined a new term that helps identify it: "scromiting," for "screaming" and "vomiting." By Wendy Fry • NBC San Diego. Published November 30, 2017 • Updated on December 8, 2017 at 2:40 pm

  • CHS, cannabis hyperemesis syndrome, occurs in patients with long term inhaled marijuana use who present with painful abdominal pain and wrenching without other identifiable causes. LaPoint J et al. Cannabinoid Hyperemesis Syndrome: Public Health Implications and a Novel Model Treatment Guidelines. West J Emerg Med. 2018;19(2):380-386. doi: 10.5811/westjem.2017.11.36368.

  • This is a report of a 27-year-old female and a 27-year-old man whose cause of death was attributed to CHS, cannabis hyperemesis syndrome. A third case of a 31year old man, CHS was appreciated, but not the cause of death Nourbakhsh M, Miller A, Gofton J, Jones G, Adeagbo B. Cannabis Hyperemesis Syndrome: Reports of Fatal Cases. J Forensic Sci. 2019;64(1):270-274. doi: 10.1111/1556-4029.13819.

  • Unraveling the Enigma of Cannabinoid Hyperemesis Syndrome (PMC, 2025) reports almost half (47.9%) of CHS patients used cannabis daily. Emergency Department Visits for Cannabis Hyperemesis Syndrome (JAMA, 2025) assesses trends among adolescents. Cannabinoid hyperemesis syndrome: A review (ScienceDirect, 2025) notes similarity to cyclic vomiting syndrome, with cessation resolving symptoms.

Cannabis Use Disorder (CUD) (Note: See Addiction / Cannabis Use Disorder for primary details)

CUD is a formal diagnosis within addiction frameworks. Additional: This study reviewed 13,588,681 people aged 14 to 65 in Ontario, Canada without a history of schizophrenia from January 1, 2006 to December 31, 2022. In this population, 0.7% developed schizophrenia without the diagnosis of cannabis use disorder (CUD), while 8.9% developed schizophrenia with CUD.)

Cannabis Use Disorder (CUD), the clinical diagnosis of marijuana addiction, affects 9–25% of all users1, with rates escalating to 17% in adolescents2 and 25–50% in daily users3, leading to compulsive use despite significant impairment in health, relationships, and daily functioning. Defined by DSM-5 criteria including tolerance, withdrawal, unsuccessful quit attempts, and continued use in hazardous situations4, CUD is driven by THC's potent activation of the brain's reward system3, causing neuroadaptations in dopamine signaling and endocannabinoid pathways that reinforce dependence5.

References

Hasin et al., 2015 – Prevalence of Marijuana Use Disorders in the United States Leung et al., 2023 – Cannabis Use and Disorders Among Adolescents Volkow et al., 2014 – Adverse Health Effects of Marijuana Use American Psychiatric Association, 2013 – DSM-5: Cannabis Use Disorder Koob & Volkow, 2016 – Neurobiology of Addiction

Cardiovascular Health

  • The American Heart Association warns: The risk of coronary artery disease, heart attack or stroke goes up to 300% (odd ratio 3.1) with cannabis use, without tobacco use. Data was obtained from the Behavioral Risk Factor Surveillance Survey of 27 US states and 2 territories. Among 434,104 respondents, 4% reported daily cannabis use and 7.1% reported non-daily use. Cannabis showed a statistically significant risk for heart disease. Jeffers AM, Glantz S, Byers AL, Keyhani S. Association of Cannabis Use With Cardiovascular Outcomes Among US Adults. J Am Heart Assoc. 2024 Feb 28:e030178. doi: 10.1161/JAHA.123.030178. Epub ahead of print. PMID: 38415581.

  • This national study compared 570,000 patients ages 15-54 who were admitted to the hospital between 2010-2014 for a primary diagnosis of arrythmia (irregular heart rate). These patients were compared to 67,662,082 patients who did not have arrythmia in the hospital. Cannabis use disorder was associated with a 47%-52% increased likelihood of arrhythmia hospitalizations in the younger population and the risk of association was controlled for confounders including other substances. Atrial fibrillation was the most prevalent arrhythmia raising concerns for stroke and other embolic events. Patel RS, Gonzalez MD, Ajibawo T, Baweja R. Cannabis use disorder and increased risk of arrhythmia-related hospitalization in young adults. Am J Addict. 2021 Aug 25. doi: 10.1111/ajad.13215. Epub ahead of print. PMID: 34432919.

  • Data from 2017 and 2018 was obtained from the American Risk Factor Surveillance System survey and included 33, 173 young adults ages 18 – 44. A history of heart attack (MI – myocardial infarction) was associated with cannabis use of ore than 4 times a month, with smoking as the primary method of consumption. MI had an odd ratio of 2 times higher among cannabis users relative to non-users. Ladha KS, et al. Recent cannabis use and myocardial infarction in young adults: a cross-sectional study. CMAJ Sep 2021, 193 (35) E1377-E1384; DOI: 10.1503/cmaj.202392

  • A review of the literature resulted in several conclusions on marijuana and cardiac health. Patients with a history of coronary artery disease should be advised against using marijuana due to increased angina symptoms. There is a 4.8 fold increase risk of heart attack risk induced by marijuana by one study, and not verified by additional investigators. Franz, CA and Frishman WH. Marijuana Use and Cardiovascular Disease. Cardiology in Review. 2016; 24:158-162. https://doi.org/10.1097/CRD.0000000000000103

  • This study, conducted in France, identified cannabis use as a possible risk factor for cardiovascular disease in young adults as the percentage of cannabis-related cardiovascular complications increased form 1.1% in 2006 to 3.6% in 2010. Jouanjus E, Lapeyre-Mestre M, Micallef J. Cannabis Use: Signal of Increasing Risk of Serious Cardiovascular Disorders. Journal of the American Heart Association. 2014; 3(2):np https://doi.org/10.1161/JAHA.113.000638

  • A review of 52,290,927 hospitalization of patients ages 18-29 found that 1.3% were former or current cannabis users that excluded alcohol, tobacco, cocaine, and amphetamine (669,407) and the frequency of acute heart attack (0.23% vs. 0.14%), arrhythmia (4.02% vs. 2.84%), and stroke (0.33% vs. 0.26%) were higher in cannabis users as compared to non-users. Desai R, Fong HK, Shah K, Kaur VP, Savani S, Gangani K, Damarlapally N, Goyal H. Rising Trends in Hospitalizations for Cardiovascular Events among Young Cannabis Users (18-39 Years) without Other Substance Abuse. Medicina (Kaunas). 2019 Aug 5;55(8):438. d

  • This study found a dose-dependent relationship with increased observed heart rate of 20 -30%, with a peak effect at 10-30 minutes after marijuana exposure. The exercise threshold before the onset of angina is dramatically decreased by 48% in patients with chronic stable angina, following marijuana use. Caldicott D, Holmes J, Roberts-Thomson K, Mahar L. Keep off the grass: marijuana use and acute cardiovascular events. European Journal of Emergency Medicine. 2005;(5):236–244 . https://doi.org/10.1097/00063110-200510000-00008

  • This study found that the risk of critical blockage of blood flow to the heart (myocardial infarction) onset was elevated 4.8 times over baseline in the 60 minutes after marijuana use. Mittleman A, Lewis A, Maclure B, Sherwood E, & Muller E. Triggering Myocardial Infarction by Marijuana. Circulation: Journal of the American Heart Association. 2001; 103(23):2805–2809. https://doi.org/10.1161/01.CIR.103.23.2805

  • This review article summaries the World Health Organization report from 2016 and the endocannabinoid effects on cardiovascular disease. They note that in the past decade there has been a nearly tenfold increase in the THC content or marijuana as well as increased availability of highly potent synthetic cannabinoids. These changes accompanied serious cardiovascular events, including myocardial infarction, cardiomyopathy, arrhythmias, stroke, and cardiac arrest. Pacher P, et al. Cardiovascular effects of marijuana and synthetic cannabinoids: the good, the bad, and the ugly. Nat Rev Cardiol. 2018;15(3):151-166. doi: 10.1038/nrcardio.2017.130.

  • Cocaine and/or marijuana was found in 10% of 2,097 patients with acute MI at age < 50 and associated with a significantly higher risk of cardiovascular mortality. DeFillippis EM, et al. Cocaine and Marijuana Use Among Young Adults with Myocardial Infarction. J Am Coll Cardiol. 2018;1(22):2540-2551. doi: 10.1016/j.jacc.2018.02.047

  • Researchers found that marijuana users were almost twice as likely to develop stress cardiomyopathy compared to non-users in a Nationwide Inpatient Sample of 33,343 people in the United States with stress cardiomyopathy between 2003 and 2011. Marijuana users were more likely to have a history of depression, psychosis, anxiety, alcohol use, tobacco use, and multiple substance use. American Heart Association News. Marijuana use may be linked to temporarily weakened heart muscle. American Heart Association. November 13, 2016. https://www.heart.org/en/news/2018/05/01/marijuana-use-may-be-linked-to-temporarily-weakened-heart-muscle .

  • Cardiovascular risk associated with the use of cannabis (Heart, 2025) provides a comprehensive report on harms to cardiovascular health. Whether It's Smoking or Edibles, Marijuana Is Bad for Your Heart (UCSF, 2025) finds chronic use reduces blood vessel function. New data link cannabis use and heart disease (UCLA Health, 2025) shows 29% higher heart attack risk. No Association between Cannabis Smoking and Cardiovascular Events (PMC, 2025) in veterans, but Lifetime Cannabis Use and Incident Hypertension (AHA, 2025) suggests no independent elevation but harms persist.

CBD / Cannabidiol Use Impacts

  • FDA approved the drug Epidiolex, pure CBD, for treatment in rare pediatric seizures. As part of the drug approval process, research is evaluated on the harms and benefits of the drug. The FDA issued a drug labeling warning for CBD that cautions of hepatocellular injury, or liver damage. The FDA lists CBD adverse reactions of 10% or more as somnolence, decreased appetite, diarrhea, high liver enzymes, fatigue, malaise, asthenia, rash, insomnia, sleep disorder, poor quality sleep, and infections. Epidiolex FDA package Label – Highlights of Prescribing Information.

  • CBD is broken down in the liver through the cytochrome P50 system. Medications that require this same type of liver metabolism when mixed with CBD can make the medication ineffective or toxic. For example, patients on a blood thinner can have excessive bleeding in taking their medication as prescribed but also using CBD or THC. Check your medications for interactions with CBD by entering cannabidiol in the mediation interaction checker. Check for interactions with THC by entering cannabis. Drugs.com

  • 84 CBD products were analyzed from 31 companies and found that only 31% were correctly labeled. THC was detected in 21.4% of samples up to 6.4 mg/ml. Oils were most frequently labeled correctly, at 45%. Bonn-Miller MO. Et al. Labeling Accuracy of Cannabidiol Extracts Sold Online. JAMA.2017;318(17):1708-1709

  • A state and federal task force identified 9 product samples that contained a synthetic cannabinoid, but not CBD and eight were branded as “Yolo CBD oil,” but provided no other information about the manufacturer or ingredients. Sixty percent of individuals who used the Yolo product were seen at an emergency department. Horth R et al. Notes from the Field: Acute Poisonings from a Synthetic Cannabinoid Sold as Cannabidiol - Utah, 2017–2018. MMWR. 2018;67(20):587-588.

  • Cannabidiol and Liver Enzyme Level Elevations in Healthy Adults (JAMA, 2025) found delayed onset of liver harm without symptoms. Beyond the hype: a comprehensive exploration of CBD's biological impacts (PMC, 2025) compiles processes affecting nausea, insomnia, but notes harms like seizure risks. Even low doses of CBD may cause harm to the liver (Yahoo News, 2025) from FDA study. UCSD Cannabidiol Clinical Trials for 2025 (UCSD, 2025) investigate harms in understanding effects.

Child Deaths

This is a report of a 27-year-old female and a 27-year-old man whose cause of death was attributed to CHS, cannabis hyperemesis syndrome. A third case of a 31year old man, CHS was appreciated, but not the cause of death Nourbakhsh M, Miller A, Gofton J, Jones G, Adeagbo B. Cannabis Hyperemesis Syndrome: Reports of Fatal Cases. J Forensic Sci. 2019;64(1):270-274. doi: 10.1111/1556-4029.13819. Cannabis Poisonings Are Rising, Mostly Among Kids (NYTimes, 2025) notes four deaths since 2009 judged by America's Poison Centers as likely caused by cannabis poisoning, one involving a child or teen. Cannabis poisoning among Ohio children spiked in 2024 (Health Policy Ohio, 2025). Relative Risk of All‐Cause Mortality Associated With Cannabis Use (PMC, 2025) links to increased risk but not in severe cases. Cannabis-Related Emergency Department Visits Climb in Kentucky, Especially Among Youth (KIPRC, 2025).

(Note: Additional child deaths may relate to pediatric exposures or contaminants; see those sections for more.)

Contaminations

  • Medical marijuana obtained from dispensaries does not differ in form from recreational marijuana. Twenty cannabis samples from legal dispensaries across northern California were found to have Cryptococcus, Mucor, Aspergillus, Gram-negative bacilli, Salmonella, Bacillus, Klebsiella and Enterobacter. The authors warm about infectious complications in marijuana users, especially if immunocompromised. Thompson GR et al. A microbiome assessment of medical marijuana. Clinical Microbiology and Infection. 2017;23(4):269-270.

  • A 34-year-old man presented with pulmonary aspergillosis on the 75th day after marrow transplant for chronic myelogenous leukemia. The patient had smoked marijuana heavily for several weeks prior to admission. Cultures of the marijuana revealed Aspergillus fumigatus with morphology and growth characteristics identical to the organism grown from open lung biopsy specimen. Despite aggressive antifungal therapy, the patient died with disseminated disease. Physicians should be aware of this potentially lethal complication of marijuana use in compromised hosts. Hamadeh R, Ardehali A, Locksley RM, York MK. Fatal Aspergillosis Associated with smoking contaminated Marijuana, in A Marrow Transplant Recipient. Chest. 1988;94(2):432-433.

  • New Study: High Toxins in Seized Cannabis (ASU, 2025) found 16% of samples positive for harmful mycotoxins. Massachusetts Cannabis Contamination Crisis (ArentFox, 2025) exposes federal negligence, with contaminated products sold 2024-2025. Identifying organic contaminants at trespass cannabis grows (ScienceDirect, 2025) notes pesticide residues. Notice - Cannabis Control Commission Massachusetts (MassCannabisControl, 2025) identified 544 contaminated lab samples.

Depression

  • Researchers from McGill and Oxford Universities carried out systematic review andmeta-analysis that included 23,217 individuals from 11 international studies. They found that cannabis use among adolescents is associated with significant increased risk of depression and suicidality in adulthood. The population attributable risk was found to be around 7%, which translates to more than 400,000 adolescent cases of cannabis attributed depression. Gobbi G, Atkin T, Zytynski T et al. Association of cannabis use in adolescence and risk of depression, anxiety and suicidality in young adulthood: A systematic review and meta-analysis. JAMA. 2019;76(4):426-434. doi:10.1001/jamapsychiatry.2018.4500.
  • Prospective cohort study of 967 high school students in 4 high schools in Canada demonstrated that illicit drug use was associated with increased risk of depression, suicidal ideations and suicide attempt. Heavy cannabis use alone predicted depression, but not suicidality. Rasic D, Weerasinghe S, Asbridge M, Langille DB. Longitudinal associations of cannabis and illicit drug use with depression, suicidal ideation and suicide attempts among Nova Scotia high school students. Drug Alcohol Depend. 2013;129(1-2):49-53. doi: 10.
  • National Academies of Sciences, E., Health and Medicine Division, Board on Population Health and Public Health Practice, & Committee on the Health Effects of Marijuana: An Evidence Review and Research Agenda. Recommendations to Support and Improve the Cannabis Research Agenda. In the Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research . National Academies Press. 2017, pp 395-402. Retrieved from https://www.nap.edu/read/24625/chapter/12
  • Cannabis Update 2025: Research on Depression (Psychiatry Podcast, 2025) correlates cannabis with increased likelihood of psychiatric disorders, including depression. Cannabis and psychopathology (PMC, 2025) shows mixed results on depression. The role of depression in the relationship between cannabis use (ScienceDirect, 2025) finds association independent of depression. Frequency of cannabis use and symptoms of anxiety and depression (2025) linked frequent use to elevated symptoms.

Diabetes

Past-Month Cannabis Use Among Adults With Diabetes (PMC, 2025) estimates 9.0% used cannabis, with increase from 7.7%. Cannabis use may quadruple diabetes risk (ScienceDaily, 2025) from massive study. Marijuana And Diabetes (The Healing Clinics, 2025) notes lower insulin but risks. Cannabis Use Quadruples Diabetes Risk (SciTechDaily, 2025) from 4 million adults study. Type 2 diabetes: Cannabis use linked to 4 times higher risk (MedicalNewsToday, 2025). (Note: Limited direct information in source. Related: This study found that marijuana users were almost twice as likely to develop stress cardiomyopathy compared to non-users. Stress cardiomyopathy may relate to metabolic issues, but specific diabetes links are not detailed. See Cardiovascular Health for more.)

Drop Outs

Heavy, long-term marijuana use during adolescence significantly elevates the risk of high school dropout by nearly sixfold for persistent users, as demonstrated in prospective panel studies tracking over 4,500 students from 7th grade through high school, where propensity score-adjusted analyses confirm causal links independent of baseline confounders like family background, peer influences, and concurrent alcohol or tobacco use . Overall, while bidirectional influences exist (e.g., school failure prompting use), the preponderance of evidence affirms marijuana as a key driver of educational disengagement, warranting targeted interventions like screening and early cessation support.

(Note: Limited direct information. Related to Amotivational Syndrome and Neurocognitive Effects, which may contribute to educational dropouts due to reduced initiative and cognitive impairment.)

Drug Interactions

  • Nearly 50% of CBD users experienced adverse drug events such as liver failure, sedation, sleep disturbance, infection and anemia. CBD is metabolized in the liver via the CYP3A4 enzyme and is therefore associated with numerous drug-drug interactions. Brown JD. And Winterstein G. Potential Adverse Drug Events and Drug-Drug Interactions with Medical and Consumer Cannabidiol (CBD) Use. J Clinical Medicine, July 2019. + THC is metabolized in the liver utilizing the CY3A4 and CYPP2C9 enzymes which results is numerous drug-drug interactions. For example, patients given ketaconazole, a fungal treatment medication, had 27% increase in THC and 204% increase in 11-OH-THC (an active metabolite of THC). All participants in the study reported serious adverse effect when THC was combined with ketoconazole. In addition, 35% of Caucasians have genetic alterations in their CYP2C9 enzyme, meaning they cannot metabolize THC as well resulting in higher dosage of THC in their body. Brown J. Potential Adverse Drug Events with Tetrahydrocannabinol (THC) Due to Drug -Drug Interactions. J Clinical Medicine. March 2020. Shamema Nasrin, Christy J.W. Watson, Yadira X Perez-Paramo and Philip Lazarus Cannabinoid metabolites as inhibitors of major hepatic CYP450 enzymes, with implications for cannabis-drug interactions. Drug Metabolism and Disposition September 7, 2021 * Drugs.com has an ‘Interactive Checker’ where you can check your prescription medications with cannabis (marijuana) or cannabidiol (CBD). Drugs.com lists 380 drugs with known interactions with cannabis including 26 major reactions. Common drug interactions occur with medications for pain, anxiety, sleep, seizures, depression, Parkinson’s disease, blood pressure and blood thinners. Cannabidiol (CBD) has 545 drug interactions including 10 major reactions. Drugs.com

PDMP, prescription drug monitoring programs track scheduled medications such as opioids and benzodiazepines for medication safety. States can include medical marijuana in this system which would important in detecting drug interaction and coordination of prescriptions. The PDMP TTAC complies information about PDMPs. The 2021 state survey shows that 8 PDMPs include medical marijuana in their PDMP patient reports: Arizona, Connecticut, Illinois, Louisiana, New York, North Dakota, Ohio, and Virginia.

An Overview of the Potential for Pharmacokinetic Interactions (PMC, 2025) reviews cannabis and prescription drugs harms. Review of Cannabis Pharmacology, Uses, Adverse Drug Events (MMJOutcomes, 2025) notes risk of adverse events 3-fold higher. Article Predicting in vivo cannabinoid-drug interactions (ScienceDirect, 2025) shows CBD inhibits UGTs. Prevalence of cannabis related potential medication interactions (ASCO, 2024) found 71% with non-anticancer meds. Drug Interactions Involving Cannabis Products (BPSPubs, 2024) assesses harms in persons aged 18+.

Emergency Visits

  • From 2006 – 2014, the rate of cannabis-associated ED visits increased, on average, 12.1% annually, from 12.3 to 34.7 visits per 100,000 population from Agency for Healthcare Research and Quality’s Healthcare Cost and Utilization Project Nationwide Emergency Department Sample. The Midwest region and patients 0 – 14 years had significant increases. Roehler DR, Hoots BE, Holland KM, Baldwin GT, Vivolo-Kantor AM. Trends and characteristics of cannabis-associated emergency department visits in the United States, 2006-2018. Drug Alcohol Depend. 2022 Jan 10;232:109288. * Denver, Colorado: Between January 2012 and December 2016, there were 9973 visits to the emergency department with cannabis related diagnosis, a 3-fold increase after legalization. Of these 9.3% were due to edibles. Inhaled cannabis were more likely to be associated with cannabinoid hyperemesis syndrome and edibles were more likely to be due to acute psychiatric and cardiovascular symptoms. Monte AA, et al. Acute Illness Associated with Cannabis Use, by Route of Exposure: An Observational Study. Annals of Internal Medicine. 2019 April 16;170(8):531-537. - San Diego Marijuana Prevention Initiative 2020 Report show over 29 emergency department visits a day for cannabis and a 776% increase in primary diagnosis of cannabis illness from 2008 – 2018. San Diego Marijuana Prevention Initiative, 2020. * Cannabis associated emergency department visits per 100,000 visits increased 7% monotonically annually. In the Western region visits increased from 15.4% to 26% over time. Medicare and Medicaid and uninsured patients were over 40% more likely to visit an emergency department. Shen JJ, et al. Trends and Related Factors of Cannabis Associated Emergency Department Visits in the United States: 2006 – 2014. J Addict Med. 2019;13(3):193-200.

  • Emergency Department visits, between January 2012 through December 2016, at UC Health University of Colorado, showed 9973 visits with ICD 9 or ICD 10 code for cannabis use. Visits attributed to inhaled cannabis were more likely to be for cannabinoid hyperemesis syndrome while visits attributable to edible cannabis were more likely to be due to psychiatric symptoms, intoxication and cardiovascular symptoms. Monte AA et al. Acute Illness Associated with Cannabis use, by route of exposure: An Observational Study. Ann Intern Med. 2019;170(8):531-537. Doi.org/ 10.7326/M18-2809

  • There were 39,092 hospitalizations due to cannabis harms among 32,811 unique individuals between 2003 and 2017, with a 280% increase. Rates of hospitalizations due to cannabis harms were greater in young adults, low-income individuals, and those with mental health comorbidities. Women age 15-24 experienced the largest average annual increase. Zygmunt A, Tanuseputro P, Brown C, Lima I, Rhodes E, Myran D. Changes in Rates of Hospitalizations due to Cannabis Harms in Ontario, Canada Before the Legalization of Nonmedical Cannabis: Retrospective Population-level Study Between 2003 and 2017. J Addic

  • Data from 52 Children’s Hospitals showed an increase of 13.3 fold in marijuana related hospitalizations in children under 6. Half required hospitalization, 15% required ICU care and 4% require mechanical ventilation. Colleen E. Bennett, Atheendar Venkataramani, Fred M. Henretig, Jennifer Faerber, Lihai Song, Joanne N. Wood. Recent Trends in Marijuana-Related Hospital Encounters in Young Children, Academic Pediatrics, 2021.

Emergency department visits from Ontario Canada were reviewed for 35,115 individuals aged 12 - 65 between January 2009 and December 2015. Individuals who used cannabis in the past year had a significantly higher emergency visits and hospitalizations than non-cannabis users. This study was subject of a CNN report. Vozoris NT, Zhu J, Ryan CM , et al. Cannabis use and risks of respiratory and all-cause morbidity and mortality: a population-based, data-linkage, cohort study BMJ Open Respiratory Research 2022; 9:e001216. doi: 10.1136/bmjresp-2022-001216

Cannabis-related emergency department visit rate increased significantly for adults aged ≥65 from 20.7 per 100,000 visits in 2005 to 395.0 per 100,000 ED visits in 2019, a 1804% relative increase. By race/ethnicity, older Black adults had the highest ED visit rate in 2019 and the largest absolute increase while older males had a higher ED visit rate in 2019 and a greater absolute increase than older women. Trends in emergency department visits associated with cannabis use among older adults in California, 2005–2019 Benjamin H. Han MD, Jesse J. Brennan MA, Mirella A. Orozco BA, Alison A. Moore MD, Edward M. Castillo PhD, MPH Journal of the American Geriatric Society, January 2023

The CDC analyzed data from a weekly average of 1,671 EDs consistently reporting data to the National Syndromic Surveillance Program. During December 30, 2018–January 1, 2023, a total of 539,106 cannabis-involved ED visits occurred among persons aged <25 data-preserve-html-node="true" data-preserve-html-node="true" years (64.9 per 10,000 ED visits) in the United States.During December 30, 2018–January 1, 2023, a total of 539,106 cannabis-involved ED visits occurred among persons aged <25 data-preserve-html-node="true" data-preserve-html-node="true" years (64.9 per 10,000 ED visits) in the United States. Roehler DR, Smith H IV, Radhakrishnan L, et al. Cannabis-Involved Emergency Department Visits Among Persons Aged <25 data-preserve-html-node="true" data-preserve-html-node="true" Years Before and During the COVID-19 Pandemic — United States, 2019–2022. MMWR Morb Mortal Wkly Rep 2023;72:758–765.

This study by the US FDA Center for Drug Evaluation and Research reviewed 55,941,880 beneficiaries for rates of cannabis related disorders from 2017 through 2022. Cannabis associated illness were greatest in states or territories with both adult and medical use legalization with 45.4 per 10,000, followed by areas with medical legalization, 41.5 per 10,000, compared to locations where cannabis use was illegal 27.7 per 10,000. Perez-Vilar S, Freyria Duenas P, Radin R, et al. State Cannabis Legalization and Trends in Cannabis-Related Disorders in US Older Adults, 2017 to 2022. JAMA Netw Open. 2024;7(6):e2417634. doi:10.1001/jamanetworkopen.2024.17634

Emergency Department Visits for Cannabis Hyperemesis Syndrome (JAMA, 2025) assesses trends in adolescents. Associations between cannabis-related hospital visits and psychotic disorders (ScienceDirect, 2025) show increases. Marijuana hospital visits linked to dementia diagnosis (CNN, 2025) notes 23% increased dementia risk. Hospital Visits for Cannabis Linked to Dementia Diagnoses (PsychiatryOnline, 2025) found nearly one in five over 45 with acute care for cannabis diagnosed with dementia within 10 years.

Environment

  • The energy and materials required to grow cannabis indoors was studied and quantified the corresponding greenhouse gas emissions. The analysis was performed across the United States and accounted for geographic variations in meteorological and electric grid emission data. Greenhouse gas emissions for legal cannabis ranges from 2,283 – 5,185 kg CO2-equivalent per kilogram of dried flower. Using the EPA calculator, this is equivalent to 583 gallons of gasoline consumed. Summers, H.M., Sproul, E. & Quinn, J.C. The greenhouse gas emissions of indoor cannabis production in the United States. Nat Sustain (2021). https://doi.org/10.1038/s41893-021-00691-w

This book chapter on energy use by the indoor cannabis industry quoted energy usage calculation on indoor cannabis cultivation. * Cannabis consumes 1% of the nation’s energy use – the same as driving 3 million cars. * 1 small grow house with 10 grow lights consumes as much electricity as 10 average US homes. * 1 gram joint creates 10 pounds of CO2 pollution, equivalent to running 10 10-watt LED light bults for 76 hours or driving 22 miles in a 44 mph Prius. * Each indoor grown cannabis plant is equivalent to 70 gallons of oil. * Indoor cannabis consumed 20 billion kilowatt-hours of electricity annually or 15 million metric tons of CO2 released into the atmosphere each year. This is an expenditure of $6 billion per year on energy, nationally, which amounts to 9% of California household electricity use. * CO2 emissions by the average cannabis user is 59% of total household carbon footprint in Colorado. * It is estimated that cannabis energy constitutes 3% of electricity demand in parts of Washington and 0.5-1% in Colorado. Mills, Evan and Zeramby, Scott. Energy Use by Indoor Cannabis Industry: Inconvenient Truths for Producers, Consumers, and Policymakers. The Routledge Handbook of Post-Prohibition Cannabis Research. Dominic Corva and Joshua Meisel, 2021.

IQ and Learning Disabilities

(Note: Related to Neurocognitive Effects and Memory. Cannabis use is associated with cognitive impairments, including lower IQ in heavy adolescent users. See those sections for details.)

Largest Study Ever Done on Cannabis and Brain Function (CU Anschutz, 2025) finds impact on working memory, with 63% of heavy users reduced activity. Under the Influence: Cognitive Effects of Medical Marijuana (PMC, 2025) links daily use to lower IQ in childhood. Cannabis Update 2025 (Psychiatry Podcast, 2025) discusses cognitive harms. Largest study ever done on cannabis and brain function (ScienceDaily, 2025) notes reduced activity. New research finds moderate cognitive impairments in heavy users (PsyPost, 2025).

Labeling Flaws Marketing CBD for medical purposes such as pain, depression or sleep is illegal. You can report such advertisement to the FDA using this link.

  • 75 marijuana products from 47 different brands found that only 17% were accurately labeled with 23% under labeled and 60 over labels with respect to THC levels. Vandrey R, et al. Cannabinoid Dose and Label Accuracy in Edible Medical Cannabis Products. JAMA 2015;313(24)2491-2493.
  • 84 CBD products from 31 companies found that only 30.95% were accurately labeled with 42.85% of products underlabeled and 26.19% overlabeled with respect to CBD levels. Bonn-Miller MO, Loflin MJE, Thomas BF, Marcu JP, Hyke T, Vandrey R. Labeling Accuracy of Cannabidiol Extracts Sold Online. JAMA. 2017;318(17):1708–1709. doi:10.1001/jama.2017.11909

How strong is your weed, really? Scientists say labels often mislead (ScienceDaily, 2025). Can weed labels be trusted? Study shows it depends on what you're buying (CU Boulder, 2025). Canadian cannabis oil labels rife with 'discrepancies' (MJBizDaily, 2024). Regulatory Landscape of Cannabis Warning Labels (AJPH, 2024). Top 10 Issues in the Cannabis Industry for 2025 (ArentFox, 2025) notes labeling problems.

Life Expectancy This Canadian study reviewed data of 11,622,471 individuals between 2006 and 2021 and found that within 5 years of hospital diagnosis of CUD (Cannabis Use Disorder) 3.5% died compared to 0.6% of matched controls of the general population. Cause of death had higher risk of suicide, trauma, opioid poisoning, other drug poisoning, and lung cancer. Myran DT, Pugliese M, McDonald AJ, et al. Cannabis Use Disorder Emergency Department Visits and Hospitalizations and 5-Year Mortality. JAMA Netw Open. 2025.

  • Among 121,895 participants with mean age of 55.15, heavy cannabis use and no tobacco use was associated with a cardiovascular risk mortality for females, hazard ratio 2.98. Vallée A. Heavy Lifetime Cannabis Use and Mortality by Sex. JAMA Netw Open. 2024;7(6):e2415227.

  • Habitual marijuana use among patients who had a heart attack resulted in a 29% higher death rate over the 18 years following the heart attack compared to non-users. Frost L, Mostofsky E, Rosenbloom JI, Mukamal KJ, Mittleman MA. Marijuana use and long-term mortality among survivors of acute myocardial infarction. American Heart Journal.2013; 165(2):170–175

  • 50,373 Swedish males ages 18-19 who were part of mandatory military service were followed in a death registry up to age 60. The results showed that ever users and heavy cannabis users (>50 times) during adolescence were associated with a higher mortality than never users. Manrique-Garcia, et al. Cannabis, Psychosis, and Mortality: A Cohort Study of 50,373 Swedish Men. The American Journal of Psychiatry. 2016;173(8):790-798.

The impact of cannabis use on ageing and longevity (PubMed, 2025) notes older adults use for pain but harms like accelerated aging. Brain Function Outcomes of Recent and Lifetime Cannabis Use (JAMA, 2025) suggests short- and long-term harms. Cannabis Update 2025 (Psychiatry Podcast, 2025) discusses risks. Marijuana Dependence Linked to Higher Risk of Death (NYTimes, 2025) links CUD to 10x suicide risk. Do Stoners Live Longer? (NuggMD, 2025) suggests no, with factors like genetics more influential but harms exist.

Marijuana Legalization and Health

This study of 144,698 patients from the European Union found that schizophrenia genetics was not associated with patterns of cannabis use. Regular users of high potency THC (over 10%) had the highest odds of psychotic disorder independent of schizophrenia genetics. Austin-Zimmerman, et al. The impact of schizophrenia genetic load and heavy cannabis use on the risk of psychotic disorder in the EU-GEI case control and UK Biobank studies. Psychological Medicine. December 2024.

This longitudinal study of 110,256,536 enrollees showed that States with Medical Cannabis laws had a 42.7% increase incidence of CUD and nearly double that increase in cannabis poisoning compared to states without such laws. Communities with increased access to cannabis may experience increased health care use and cost due to cannabis poisoning and CUD.

A total of 107 delta 9-THC cannabis flower samples were collected from adult commercial use cannabis dispensaries from Colorado, Oregon, and California and analyzed for cannabinoid concentration. Of the 107 samples, only 32 were found to have THC concentration within 20% accuracy of the product label. Actual concentration ranged from 12.95% to 36.55%. Geweda MM, Majumdar CG, Moore MN, Elhendawy MA, Radwan MM, Chandra S, ElSohly MA. Evaluation of dispensaries' cannabis flowers for accuracy of labeling of cannabinoids content. J Cannabis Res. 2024 Mar 9;6(1):11

  • A Rand corporation study of 1,887 people age 18-22 who live in Los Angeles, if they live in a neighborhood with a higher number of medical marijuana dispensaries, they use pot more frequently and have a more positive view about the drug. Shih RA, Rodriguez A, Parast L et al. Associations Between Young Adult Marijuana Outcomes and Availability of Medical Marijuana Dispensaries and Storefront Signage. Addiction. 2019;114(1):1-22. * Study of 32 Oregon countries from 2006 to 2015 showed higher marijuana use by youth with higher registered marijuana patients and growers. Paschall MJ, Grube JW, Biglan AB. Medical Marijuana Legalization and Marijuana Use Among Youth in Oregon. J Prim Prev. 2017;38(3):329-341. * Federal Regulation of Cannabis for Public Health White Paper from USC Shaeffer Center for Health Policy and Economics haven several Key Takeaways * Long-term or heavy use of cannabis—in particular, high-potency manufactured cannabis products—is associated with negative health outcomes, including psychosis, cannabis hyperemesis and addiction. * Vermont and Connecticut are the only states that cap potency of THC on most types of cannabis products sold, despite this being a useful tool to prevent harmful consumption. * Assuming a standardized dose of 10 milligrams of THC for average-potency cannabis products, all states allow purchases exceeding 500 doses. Current sales restrictions do not promote moderation in use. * Taxes based on potency, rather than price or weight, do a better job of incentivizing moderate THC consumption. * A single, federal, seed-to-sale tracking system will assist with enforcement of all policies and aid in public health research, particularly given the restrictions in place on scientific inquiry of these products. Pacula RL. et al. Federal Regulation of Cannabis for Public Health in the United States. July 2022

700 legal cannabis dispensaries in California were evaluated between June 2019 and September 2019 showing that 67.9% of these dispensaries failed to comply with California laws requiring age-limit signage. 35.3% broke the law by having marketing items that appealed to children inside their stores. Shi Y, Pascula RL, Assessment of Recreational Cannabis Dispensaries' Compliance With Underage Access and Marketing Restrictions in California. JAMA Pediatrics. August 2021.

This study reviewed 13,588,681 people aged 14 to 65 in Ontario, Canada without a history of schizophrenia from January 1, 2006 to December 31, 2022. In this population, 0.7% developed schizophrenia without the diagnosis of cannabis use disorder (CUD), while 8.9% developed schizophrenia with CUD. The population-attributable risk factor for CUD associated with schizophrenia tripled from 3.7% to 10.3% with cannabis legalization. This risk was up to 18.9% for males aged 19 -24 years. The annual incidence of schizophrenia was stable over time. The incidence of psychosis not otherwise specified (NOS) increased from 30 to 44.1 per 100,000 individuals, or 83.7% Myran DT, et al. Changes in Incident Schizophrenia Diagnosis Associated With Cannabis Use Disorder After Cannabis Legalization. JAMA Netw open.

Recreational cannabis legalization: Potential implications for health (CCJM, 2025) evaluates increased consumption, crime, traffic safety harms. A quantitative projection of the net health effects of cannabis (NIH, 2025) notes 1–2% of new users develop long-term mental health problems. Public Health Consequences of Changes in the Cannabis Landscape (National Academies, 2025) states consequences not comprehensively evaluated. 9 facts about Americans and marijuana (Pew, 2025) notes 27% say legalization decreases other drug use, but 29% say increases. Cannabis: Health, Research and Regulatory Considerations (AAFP, 2025) discusses decriminalization but health harms.

Mass Murder

(Note: No direct studies in source material linking cannabis to mass murder. Related to Psychosis, Violence, and Schizophrenia, where cannabis-induced psychotic episodes may contribute to violent acts in rare cases. See those sections for indirect evidence.)

Cannabis involvement and mass shooting events (EASAP, 2024) found cannabis use significantly higher in mass shootings from 1996 onward. What the Data Really Say About Cannabis and Crime (YouTube, 2025) discusses crime fall post-legalization but harms. Study links cannabis dependence with higher death risk (HealthPolicyOhio, 2025) notes suicide risks. Research Roundup May 2025 (CannabisScienceTech, 2025) links high usage to increased mortality in colon cancer, but not mass murder. Exploring Cannabis and Mortality (HighScience, 2025) separates myth from reality on deaths.

Medical Organization Position Statements

  • The Association for Addiction Professionals does not support the use of cannabis as medicine or for recreational purposes. * Cannabis needs to be subject to the same research, consideration, and study as any other medicine through the FDA. NAADAC Position Statement on the Medical and Recreational Use of Cannabis

  • Medical research does not support cannabis-based products as treatment options for the majority of neurological disorders. * Psychiatric and neurocognitive adverse effects have been described in recreational and medical use, which is particularly problematic in a population with compromised neurological function. * The interaction of cannabis products and neurological prescriptions is uncertain. AAN Position: Use of Medical Cannabis for Neurological Disorders. American Academy of Neurology. Updated in 2020.

  • “Based on reviews by the National Eye Institute (NEI), the Institute of Medicine (IOM), and on available scientific evidence, the American Academy of Ophthalmology Complementary Therapy Task Force finds noscientific evidence demonstrating increased benefit and/or diminished risk of marijuana use in the treatment of glaucoma compared with the wide variety of pharmaceutical agents now available.” American Academy of Ophthalmology Complementary Therapy Task Force. Marijuana in the Treatment of Glaucoma TA – 2014.

  • AAP opposes marijuana use in ages 0 – 21 due to negative effects on the developing brain. - AAP opposes “medical marijuana” outside the regulatory process of the US FDA - AAP discourages the use of marijuana by adults in the presence of minors - AAP strongly opposes the use of smoked marijuana because smoking is known to cause lung damage. Committee on Substance Abuse, Committee on Adolescence. The Impact of Marijuana Policies on Youth: Clinical, Research, and Legal Update. Pediatrics. March 2015, Volume 135, Issue 3.

  • The American Cancer Society opposes the smoking or vaping of marijuana and other cannabinoids in public places because the carcinogens in marijuana smoke pose numerous health hazards to the patient and others in the patient’s presence. American Cancer Society – Marijuana and Cancer, revised August 4, 2020

On October 24, 2021 the American College of Emergency Physicians, ACEP, passed a resolution on the Complications of Marijuana Use. This resolution directs ACEP to develop practice guidelines on the treatment and complications of marijuana use as seen in emergency department presentations, that ACEP provide education and guidance to emergency physicians in relationship to documentation and overall awareness of cannabis related ED diagnosis, and that ACEP develop and disseminate public facing information on the complications of marijuana use as seen in the emergency department. Click to read the resolution.

  • ACMT calls upon stakeholders to implement measures to prevent cannabis exposure in children less than 12. Amirshahi MM, et al. ACMT Position Statement: Addressing Pediatric Cannabis Exposure. Journal of Medical Toxicology. March 2019.

  • OBGYN should be discouraged from prescribing or suggesting the use of marijuana for medical purposes during preconception, pregnancy, and lactation. Committee on Obstetric Practice. Committee Opinion No. 722 Summary: Marijuana Use During Pregnancy and Lactation. Obstetrics & Gynecology. October 2017.

The American Dental Association points out several oral health risks associated with cannabis smoking. This includes gum disease (periodontal complications), dry mouth (xerostomia), and white plaques in the mouth (leukoplakia) as well as increased risk of mouth and neck cancers. American Dental Association. Cannabis Oral Health Effects. August 2020.

  • Over 3 million Americans live with epilepsy * The term “medical marijuana” is a legal definition * Purified CBD, available by prescription as Epidiolex may be effective in treatment of Lennox-Gastaut syndrome and Dravet syndrome. * The purified, pharmaceutical formulation of CBD cannot be obtained from a marijuana dispensary. Products from a dispensary may not contain just CBD, but also THC, pesticides, bacteria, and other dangerous impurities. American Epilepsy Society Position Statement on Cannabis as a Treatment for Epileptic Seizures. Feb 19, 2019.

  • Marijuana or its components are not recommended for the treatment of glaucoma due to lack of evidence, short duration of action in lowering intraocular pressure, and lack of long-term trials that evaluate the health of the optic nerve. American Glaucoma Society Position Statement: Marijuana and the Treatment of Glaucoma

  • Patients with underlying heart disease could experience increase angina when cannabis is smoked. * Continual cannabis use is associated with increased risk of metabolic syndrome compared to no use. * The risk of stroke was higher among frequent marijuana users age 18 – 44 with concomitant e-cigarette use. * The public needs high quality information about cannabis, which can help counterbalance the proliferation of rumor and false claims about the health effect of cannabis products. * There is a need to create knowledge and automated warnings around drug-drug interactions. Page RL, et al. Medical Marijuana, Recreational Cannabis, and Cardiovascular Health: A Scientific Statement From the American Heart Association. Circulation. 2020.

    • Smoke from marijuana combustion has the same toxins, irritants and carcinogens as tobacco smoke. * Marijuana smokers have a greater exposer of tar per breath than tobacco smokers. * Smoking marijuana clearly damages the human lung, and regular use leads to chronic bronchitis and can cause an immune-compromised person to be more susceptible to lung infections. * No one should be exposed to secondhand marijuana smoke. Secondhand marijuana smoke contains the same toxins and carcinogens found in directly inhaled marijuana smoke, in similar amounts if not more. * The American Lung Association strongly cautions the public against smoking marijuana as well as tobacco products. American Lung Association. Marijuana and Lung Health. December 17, 2020.

  • Cannabis is a dangerous drug and as such is a serious public health concern * The sale of cannabis for adult use should not be legalized * States that have legalized cannabis for medical or adult use should be required to take steps to regulate the product and protect public health and safety AMA Policy. Cannabis Legalization for Adult Use (commonly referred to as recreatio...(truncated 21225 characters)..., remember, and control emotions and behavior. Crean RD, Crane NA, Mason BJ. An evidence-based review of acute and long term effects of cannabis use on executive cognitive function. J Addict Med. 2011;5(1):1-8. Doi.org/ 10.1097/ADM.0b013e31820c23fa.

  • Marijuana use was associated with increased impulsivity on the same day and the follow day relative to days when marijuana was not used, independent of alcohol use, in 43 participants without SUD. Ansell EB, et al. Effects of marijuana use on impulsivity and hostility in daily life. Drug and Alcohol Dependence. 2015;148(136-142). https://www.sciencedirect.com/science/article/abs/pii/S0376871614020092?via%3Dihub

  • MRI imaging of the brain was compared in marijuana users in Switzerland in male volunteers age 18 – 30. Battistella G et al. Long-term effects of cannabis on brain structure. Neuropsychopharmacology. 2014;(9):2041-2048.

Memory

MRI imaging of the brain was compared in marijuana users in Switzerland in male volunteers age 18 – 30. Battistella G et al. Long-term effects of cannabis on brain structure. Neuropsychopharmacology. 2014;(9):2041-2048.

Largest Study Ever Done on Cannabis and Brain Function (CU Anschutz, 2025) finds 63% of heavy users reduced activity during memory tasks. Brain Function Outcomes of Recent and Lifetime Cannabis Use (JAMA, 2025) associates with poorer performance. Brain Function Outcomes (PubMed, 2025) notes lower activation in memory tasks. Weeding Out the Truth (Penn Memory Center, 2025) discusses reduced activity. Largest study ever done on cannabis and brain function (ScienceDaily, 2025).

Motor Vehicle Collisions & Deaths

(Note: Source material mentions Motor Vehicle Crashes but not explicitly detailed. Related: Habitual marijuana use is associated with cognitive impairments that may increase crash risk; see Neurocognitive Effects.)

Over 40% of Deceased Drivers in Motor Vehicle Crashes Test Positive for THC (FACS, 2025). New Study Finds Cannabis Use Impacting Vehicle Crashes (AASHTO, 2025) notes 41.9% positive for THC. Weed, THC, Car Crashes, and Fatalities (Psychology Today, 2025) cites 33% positive. Nearly half of drivers killed in crashes had THC (ScienceDaily, 2025). Relationships of Changing State Cannabis Policies With Alcohol (AJPM, 2025) associates restrictive policies with reduced fatalities.

Neonatal Exposure

Dramatic increases in cannabis use during pregnancy are alarming because of evidence that prenatal exposure may be associated with a host of adverse outcomes. 1 We previously found that prenatal cannabis exposure (PCE) following maternal knowledge of pregnancy is associated with increased psychopathology during middle childhood using baseline data from the Adolescent Brain Cognitive Development (ABCD) study. 2 Here, leveraging longitudinal ABCD study data (data release 4.0), we examined whether associations with psychopathology persist into early adolescence. Baranger DAA, Paul SE, Colbert SMC, et al. Association of Mental Health Burden With Prenatal Cannabis Exposure From Childhood to Early Adolescence : Longitudinal Findings From the Adolescent Brain Cognitive Development (ABCD) Study. JAMA Pediatr. 2022;176(12):1261–1265. doi: 10.1001/jamapediatrics.2022.3191

This cross-sectional analysis of 11,489 children age 9 – 11 from 22 sites across the United States between 2016 and 2018 showed increased risk of psychosis and psychopathology in children whose mothers used cannabis while pregnant. This was part of the ABCD longitudinal study. Paul SE, Hatoum AS, Fine JD, et al. Associations Between Prenatal Cannabis Exposure and Childhood Outcomes: Results From the ABCD Study. JAMA Psychiatry. 2021;78(1):64–76. doi:10.1001/jamapsychiatry.2020.2902

Meta-analysis of maternal and neonatal outcomes of cannabis use (PMC, 2025) shows worse outcomes. A systematic review investigating prenatal cannabis and tobacco co (ScienceDirect, 2025) notes long-term behavioral harms. Cannabis Use During Pregnancy and Lactation (ACOG, 2025) associates with low birth weight, NICU admission. Is Prenatal Cannabis Use Associated with Adverse Neonatal (JWatch, 2025) finds heightened risk. In utero chronic cannabis exposure is associated with lower brain volume (Taylor & Francis, 2025).

Neurocognitive Effects

  • Marijuana use was associated with increased impulsivity on the same day and the follow day relative to days when marijuana was not used, independent of alcohol use, in 43 participants without SUD. Ansell EB, et al. Effects of marijuana use on impulsivity and hostility in daily life. Drug and Alcohol Dependence. 2015;148(136-142). https://www.sciencedirect.com/science/article/abs/pii/S0376871614020092?via%3Dihub

  • MRI imaging of the brain was compared in marijuana users in Switzerland in male volunteers age 18 – 30. Battistella G et al. Long-term effects of cannabis on brain structure. Neuropsychopharmacology. 2014;(9):2041-2048.

Brain Function Outcomes of Recent and Lifetime Cannabis Use (JAMA, 2025) shows diminished activation and performance. Brain Function Outcomes (PubMed, 2025) associates with poorer performance in memory and motor tasks. Largest Study Ever Done on Cannabis and Brain Function (CU Anschutz, 2025) finds impact on working memory. Cognitive Effects of Cannabis Use (MDPI, 2025) points to impairments in encoding and false memory. Cognitive performance in young adults with CUD (ScienceDirect, 2025) shows worse performance.

Pain and Opioids

This publication in the peer review medical journal publishes review articles in the field of anesthesia. Their conclusion for using cannabis for acute pain was: Th e scientific basis for supporting the use of cannabis is extensive, although it does not necessarily translate into relevant clinical outcomes. The use of cannabinoids in acute pain did not always consistently show statistically significant results in improving acute pain. Botea MO. et al. Cannabinoids for Acute Pain Management: Approaches and Rationale. Acute Pain and Headache Reports. 2024.

  • This toxicology test book states that studies examining the efficacy of cannabis in the setting of induced acute pain showed no improvement. Smoked marijuana failed to attenuate thermal pain in volunteers, and an oral THC analog have no effect on postsurgical pain. Cannabinoids have some favorable outcomes when used to treat chronic neuropathic pain, although design flaws severely limit the quality of medical evidence. Lapoint J. Cannabinoids. In: Weitz M and Naglieri C, eds. Goldfrank’s Toxicologic Emergencies. 10 th ed. China: McGraw-Hill; 2002. * 18 healthy women were given oral cannabis verses placebo for a sunburn pain. They had no pain relief with pot and some developed hyperalgesia, worsening pain. Kraft B, Oral Cannabis Ineffective in Treating Acute Pain. J Anesthesia, 2008 + 15 volunteers were given capsaicin to induce pain and the treated with either high, medium, low, or no smoke marijuana. The group with medium marijuana dose had less pain, but the group with high dose marijuana had increased pain. Cannabis and Pain: A Clinical Review. Hill et al. Cannabis Cannabinoid Res. 2017 - The largest study that claims that marijuana is good for pain is based on a publication by Whiting in 2015. This publication reviewed 28 studies with 2,454 patients and compared cannabis vs placebo. They found a pain reduction in 37% of cannabis patients compared to 31% in placebo, a 6% difference. However, most of the studies that claimed improved in pain were based on neuropathic pain, not traditional pain. Furthermore, the cannabis group suffered from more serious adverse effects. - Studies that show marijuana is helpful for pain use low dose THC, low number of patients and do not balance the risks Whiting PF, et al. Cannabinoids for Medical Use: A systematic Review and Meta-analysis. JAMA, 2015 * 10 Advance Cancer patients were given THC pills vs placebo and reported pain relief with high doses at 15 – 20 mg. However, these same patients who claimed pain relief also became very sedated and had disorganized thoughts. They author then repeated the study and compare THC to codeine and found no difference in pain relief. 5 patients had to be excluded from the study because they developed severe anxiety after receiving THC. Noyles R, et al. Analgesic effect of delta-9-tetracannbinol and codeine. Clinical Pharmacology and Therapeutics. 18:84-89 Noyles R, et al. Analgesic effect of delta-9-tetracannbinol. Journal of Clinical Pharmacology, 15:139-143.

  • This study followed 1514 participants with chronic non-cancer pain over 4 years and found that cannabis using participants had a greater pain severity score, greater pain interference score, lower pain self-efficacy scores, and greater generalized anxiety disorder severity scores compared to those who did not use cannabis. The researchers found no evidence of temporal relationship between cannabis use and pain severity or pain interference, and no evidence that cannabis use reduced prescribed opioid use or increased rates of opioid discontinuation. Campbell G et al. Effect of cannabis use in people with chronic non-cancer pain prescribed opioids: findings from a 4-year prospective cohort study. The Lancet Public Health. 2018;3(7):e341-e350.

  • Using marijuana during opioid treatment increases the risk that opioid treatment would be unsuccessful. Larkin PJ, Madras BK. Opioids, overdoses, and cannabis: is marijuana an effective response to the opioid abuse epidemic? The Georgetown Journal of Law and Public Policy. - 371 people with long term opioid therapy were evaluated for medical cannabis use. The medical cannabis users had higher scores or risk for prescription opioid misuse, rates of hazardous alcohol use, and rates of nicotine use. Nugent SM. Et al. Patterns and correlates of medical cannabis use of pain among patients prescribed long term opioid therapy. Gen Hosp Psychiatry 2018. * The book Marijuana as Medicine? The Science Beyond the Controversy reviews several studies on cannabis and pain and finds significant harms with inconsistent benefit. Marijuana as Medicine? The Science Beyond the Controversy. Alison Mack, Janet Joy. - The authors of this article conclude that the unsettling safety profile of cannabis, the lack of strong empirical support for its efficacy, the general absence of CBD in what is used “medically,” and the methodological challenges in conducting research suggest that, at present, cannabis should not necessarily be considered an optimal choice as a drug for pain management Cannabis for Chronic Pain: Not Ready for Prime Time. Carr and Schatman. Am J Public Health

  • This large study used the National Survey on Drug Use and Health, NSDUH, data from 2015 and found that medical marijuana users were significantly more likely to report medical use of prescription drugs and more likely to report nonmedical use of prescription drugs in the past 12 months of any prescription drug. Caputi L, Humphreys L. Medical Marijuana Users are More Likely to Use Prescription Drugs Medically and Nonmedically. Journal of Addiction Medicine. 2008;12(4):295–299.

  • This study of 209 patients between 2011 and 2014 found that participants with cannabis in their initial urine drug toxicology were more likely to have a future occurrence of an opioid misuse, have a history of substance abuse, and more likely to have a future occurrence of an opioid related aberrancy. Dibenedetto D, Weed V, Wawrzyniak K, Finkelman M, Paolini J, Schatman M, Kulich R. The Association Between Cannabis Use and Aberrant Behaviors During Chronic Opioid Therapy for Chronic Pain. Pain Medicine. 2017; 19(10):1997-2008.

  • A PubMed review of 2,237 titles resulted in 14 studies that met inclusion criteria to review and found cannabis use ranging 6.2 – 38% in chronic opioid users compared to 5.8% in general population. Cannabis use in chronic opioid patients shoed statistically significant associations with present and future aberrant opioid-related behaviors. Reisfield GM et al. The Prevalence and Significance of Cannabis Use in Patients Prescribed Chronic Opioid Therapy: A Review of the Extant Literature. Pain Med. 2009;(8):1434-41.

  • Data from 34,653 participants from the National Epidemiologic Survey on Alcohol and Related Conditions, from 2001-2002 compared to 2004-2005, showed that cannabis use increased the risk of developing nonmedical prescription opioid use and opioid use disorder. Olfson M, Wall M, Liu S, Blanco C. Cannabis Use and Risk of Prescription Opioid Use Disorder in the United States. American Journal of Psychiatry. 2017; 175(1):47–53.

  • The United States opioid mortality rate was compared in states and District of Columbia that had implemented marijuana legalization with states that had not. Variables included race/ethnicity and fentanyl-type opioids. The COVID-19 pandemic increase marijuana use and worsened opioid mortality. Archie Bleyer, Brian Barnes, Kenneth Finn. United States marijuana legalization and opioid mortality epidemic during 2010–2020 and pandemic implications, Journal of the National Medical Association, 2022, ISSN 0027-9684. * This study debunks bad science published by Bauchheber et all in JAMA where they found that from 1999-2010 states with medical cannabis laws experienced slower increases in opioid analgesic overdose mortality. They claimed that medical marijuana laws were protective in opioid overdoses. However, the study used data before legalization was expanded. When the same exact study was repeated extending the data from 1999 – 2017, the results showed the opposite association from the initial flawed study. States passing a medical cannabis law experienced a 22.7% increase in overdose deaths. Shover CL, Davis CS, Gordon SC, Humphreys K. Association between medical cannabis laws and opioid overdose mortality has reversed over time. PNAS. 2019;116(26):12624-12626. - Bleyer debunks the “marijuana protection hypothesis.” He evaluated opioid mortality in all states and the District of Columbia through 2017 and showed that the 23 legalizing states had a 78% statistically significant acceleration of opioid death rates after medical or recreational legalization. Bleyer, A and Barnes, B. Contribution of Marijuana Legalization to the U.S. Opioid Mortality Epidemic: Individual and Combined Experience of 27 States and District of Columbia. * Hsu and Kovacs published bad science in the British Medical Journal in 2021 claiming that increased number of cannabis store fronts correlates with decreased opioid deaths in that county zip code in the 23 states that have legalized marijuana. While the study showed nice graphs and calculations, they failure to zoom out to the big picture of what is happening in the total state and compare to all the states.

  • The American Society of Addiction Medicine, ASAM, states that cannabis should not be used to treat opioid use disorder. This follows the studies that show increased misuse of opioids without improvement of pain in people who use cannabis. American Society of Addiction Medicine. Cannabis Policy Statement. October 10, 2020.

  • Systemic review and meta-analysis of six randomized controlled trials included 1442 participants with cancer related pain and low risk of bias. The studies showed no difference between cannabinoids and placebo in pain scores. Cannabinoids had a higher risk of adverse events when compared to placebo, especially dizziness and somnolence. Boland EG, Bennett MI, Allgar V, Boland JW. Cannabinoids for adult cancer-related pain: systematic review and meta-analysis. BMJ Support Palliat Care. 2020 Mar;10(1):14-24. doi: 10.1136/bmjspcare-2019-002032. Epub 2020 Jan 20. PMID: 31959586.

  • 26 adolescent/young adults ages 14 – 22 met the criteria of opioid use disorder and used marijuana to get and high and a belief that smoking marijuana will help them not return to opiate use. In all cases, marijuana use failed to stop opioid addiction and facilitated their return to heavy opioid use. Steven L. Jaffe. Case Reports on the Failure of Smoking Marijuana to Prevent Relapse to Use of Opiates in Adolescents/Young Adults With Opiate Use Disorder. Emerging Trends in Drugs, Addictions, and Health, Volume 1,2021. 100011,ISSN 2667-1182, https://doi.org/10.1016/j.etdah.2021.100011.

  • Lack of Science + Increased Opioid Use + Addiction + Withdrawal + Risk/Benefit Calculation Lev, Roneet. Pain and Pot presentation to the Prevention Technology Transfer Center, March 10, 2021

A strong placebo response may be largely responsible for the significant pain reduction observed in clinical trials of cannabis-based therapies, results of a new meta-analysis suggest. https://www.medscape.com/viewarticle/985360

Data from 12 states with medical cannabis laws were compared to 17 states without such laws reviewing 583,820 commercially insured adults with chronic non cancer pain. Medical cannabis law showed no effect on opioid and non-opioid chronic pain treatment. McGinty EE, Tormohlen KN, Barry CL, Bicket MC, Rutkow L, Stuart EA. Protocol: mixed-methods study of how implementation of US state medical cannabis laws affects treatment of chronic non-cancer pain and adverse opioid outcomes. Implement Sci. 2021 Jan 7;1

Full-spectrum extract from Cannabis sativa for chronic low pain (Nature, 2025) shows efficacy but harms like increased opioid use. Cannabis Versus Opioids for Pain (StatPearls, 2023, updated 2025) notes harms in chronic pain. ACOEM Cannabis guideline (DIR.ca.gov, 2025) discusses no reduction in opioid use. The relationship of medical and recreational cannabis laws with opioids (ScienceDirect, 2025) examines stratified harms.

Pancreatitis

  • Cannabis has been increasingly implicated as a cause of acute pancreatitis. Pancreatitis is inflammation of the pancreas that results in severe abdominal pain. It can be caused by alcohol, gallstones, various drugs, infections, and other conditions. Pancreatitis caused by cannabis was first reported in the medical literature in 2004, and since there have been multiple cases described. Singh, Rohit MD; Torre, Kristin MD; Saba, Marian MD; Stepczynski, Jadwiga MD Cannabis-induced Pancreatitis, Pancreas: August 2020 - Volume 49 - Issue 7 - p e66-e67 doi: 10.1097/MPA.0000000000001605

Pediatric Exposures Increased marijuana poisoning in children follows increased availability and increased potency. Visit any cannabis store in person or on-line and you will find concentrates at over 90% THC. High potency THC can behave like a hard drug, like methamphetamine. Dosing in children is a major concern. One gummy of 10 mg THC for an adult can cause psychosis. For a child it can cause altered mental status, encephalopathy, or delirium. Roneet Lev, MD FACEP. Marijuana Candy: Poisoning and Lack of Protection for Children February 1, 2023

  • In a study of 52 Children’s hospital from 2004 – 2018, 1296 patients age 5 and under were found to have hospital visits due to cannabis exposure. This reflected a 13.3 increase of cases over time. 15% of patient required ICU care and 4% required mechanical ventilation. Bennett CE, Venkataramani A, Henretig FM, Faerber J, Song L, Wood JF. Recent Trends in Marijuana-Related Hospital Encounters in Young Children. Acad Pediatr. 2021 Jul

  • Children age 10 or less were evaluated for marijuana exposure between 2009 and 2015 with 81 children treated at the children’s hospital and 163 consulted at the regional poison center. The median age of the children was 2. The annual poison center calls for child marijuana exposure increased 5-fold since legalization I the state. Edibles were responsible for 52% of the exposures. Wang GS et al. Unintentional Pediatric Exposures to Marijuana in Colorado, 2009-2015.

  • One in six toddlers between the age of one month and 2 years who were admitted to Children’s Hospital Colorado between January 2013 and April 2014 with bronchitis, tested positive for THC metabolites. Positive marijuana exposure in the toddlers went up to 21% post legalization from 10% before legalization. American Academy of Pediatrics. "One in six children hospitalized for lung inflammation positive for marijuana exposure: Few states where marijuana use is legal restrict its use around children." ScienceDaily. ScienceDaily, 30 April 2016.

  • Urine samples were obtained from children who were hospitalized in Colorado and had a parent participating in a smoking cessation study. All children ahd urine samples that were analyzed for cotine (tobacco metabolize) and 11-hydroxy-delta9-tetrahydrocannabinol (COOH-THC, a marijuana metabolite.) Approximately half of the children in the study had biological evidence of exposure to marijuana. Wilson KM, et al. Marijuana and Tobacco Coexposure in Hospitalized Children.

Dramatic increases in cannabis use during pregnancy are alarming because of evidence that prenatal exposure may be associated with a host of adverse outcomes. 1 We previously found that prenatal cannabis exposure (PCE) following maternal knowledge of pregnancy is associated with increased psychopathology during middle childhood using baseline data from the Adolescent Brain Cognitive Development (ABCD) study. 2 Here, leveraging longitudinal ABCD study data (data release 4.0), we examined whether associations with psychopathology persist into early adolescence. Baranger DAA, Paul SE, Colbert SMC, et al. Association of Mental Health Burden With Prenatal Cannabis Exposure From Childhood to Early Adolescence : Longitudinal Findings From the Adolescent Brain Cognitive Development (ABCD) Study. JAMA Pediatr. 2022;176(12):1261–1265. doi: 10.1001/jamapediatrics.2022.3191

In this cohort study of 1087 participants who reported cannabis use in the previous year, after adjusting for frequency of cannabis use and early adolescent mental health, use of high-potency cannabis was associated with a significant increase in the frequency of cannabis use, likelihood of cannabis problems, and likelihood of anxiety disorder. Those using high-potency cannabis had a small increase in the likelihood of psychotic experiences; however, this risk was attenuated after adjustment for frequency of cannabis use. Hines LA, Freeman TP, Gage SH, et al. Association of High-Potency Cannabis Use With Mental Health and Substance Use in Adolescence. JAMA Psychiatry. 2020;77(10):1044–1051. doi: 10.1001/jamapsychiatry.2020.1035

Legalization of medical and recreational cannabis is a major contributor to pediatric cannabis exposures. The trends and magnitude of pediatric cannabis exposures in Michigan after medical cannabis legalization in 2008 have not been assessed. DOI: https://doi.org/10.1016/j.jemermed.2020.12.028

Earlier age at drug initiation has been shown to be associated with faster transition to substance use disorder (SUD). 1 However, prevalence of specific SUDs as a function of time since first substance use among young people has not, to our knowledge, been investigated. We examined the prevalence of specific SUDs since first drug use (including tobacco, alcohol, cannabis, cocaine, methamphetamine, and heroin) or prescription misuse (including opioids, stimulants, and tranquilizers) in adolescents aged 12 to 17 years and young adults aged 18 to 25 years. Volkow ND, Han B, Einstein EB, Compton WM. Prevalence of Substance Use Disorders by Time Since First Substance Use Among Young People in the US. JAMA Pediatr. 2021;175(6):640–643. doi: 10.1001/jamapediatrics.2020.6981

The National Poison Data System data for pediatric calls about edible cannabis products in children <6 data-preserve-html-node="true" data-preserve-html-node="true" years noted 7043 exposures between 2017–2021. In 2017, there were 207 reported cases, and in 2021 there were 3054 cases, an increase of 1375.0%. Most exposures (97.7%) occurred in a residential setting. Seventy percent of cases followed to a known outcome were reported to have central nervous system depression. Of all reported cases, 22.7% of patients were admitted to the hospital. There was a significant increase in both ICU and non-ICU admissions. Marit S. Tweet, Antonia Nemanich, Michael Wahl; Pediatric Edible Cannabis Exposures and Acute Toxicity: 2017–2021. Pediatrics February 2023; 151 (2): e2022057761. 10.1542/peds.2022-057761

Cannabis Use in Adolescents (PMC, 2025) notes perceived risk decline. Cannabis and pediatric cannabis exposure (ACAMH, 2025) shows increased exposures in young children. Cannabis Poisonings Are Rising (NYTimes, 2025) discusses symptoms like seizures. Characteristics and Trends in Child Cannabis Exposures (AJPM, 2025) examines changes. Temporal Association Between Cannabis Legalization and Pediatric Exposures (AAP, 2025) notes quarterly increases.

Psychosis This study of 144,698 patients from the European Union found that schizophrenia genetics was not associated with patterns of cannabis use. Regular users of high potency THC (over 10%) had the highest odds of psychotic disorder independent of schizophrenia genetics. Austin-Zimmerman, et al. The impact of schizophrenia genetic load and heavy cannabis use on the risk of psychotic disorder in the EU-GEI case control and UK Biobank studies. Psychological Medicine. December 2024.

This study reviewed 13,588,681 people aged 14 to 65 in Ontario, Canada without a history of schizophrenia from January 1, 2006 to December 31, 2022. In this population, 0.7% developed schizophrenia without the diagnosis of cannabis use disorder (CUD), while 8.9% developed schizophrenia with CUD. The population-attributable risk factor for CUD associated with schizophrenia tripled from 3.7% to 10.3% with cannabis legalization. This risk was up to 18.9% for males aged 19 -24 years. The annual incidence of schizophrenia was stable over time. The incidence of psychosis not otherwise specified (NOS) increased from 30 to 44.1 per 100,000 individuals, or 83.7% Myran DT, et al. Changes in Incident Schizophrenia Diagnosis Associated With Cannabis Use Disorder After Cannabis Legalization. JAMA Netw open.

  • This population-based data included 11, 363 records of universal healthcare patient in Ontario, Canada from 2009 to 2018. Compared to no cannabis use, cannabis use was associated with 11 fold risk of psychosis for ages 12 - 19 based on hospitalizations and ED visits. McDonald AJ, Kurdyak P, Rehm J, Roerecke M, Bondy SJ. Age-dependent association of cannabis use with risk of psychotic disorder. Psychol Med. 2024 May 22:1-11.

  • The World Federation of Societies of Biological Psychiatry Task Force reviewed the literature of liberalization of cannabis laws and the risk of psychosis. The concluded that delaying or eliminating cannabis exposure can decrease the rate of psychosis related to cannabis. Deepak CJ, DiFort M, et al. Consensus paper of the WFSBP task force on cannabis, cannabinoids and psychosis, The World Journal of Biological Psychiatry, 2022. * 6,907,859 individuals from Denmark were evaluated for the association of cannabis use disorder and schizophrenia. Among age 16 - 20, males were twice an likely than females to develop schizophrenia in the setting of cannabis use disorder. 30% of schizophrenia diagnosis could have been prevented, about 3000 cases, in men age 21-30 if they did not have a cannabis use disorder. Hjorthøj, C., Compton, W., Starzer, M., Nordholm, D., Einstein, E., Erlangsen, A., . . . Han, B. (2023). Association between cannabis use disorder and schizophrenia stronger in young males than in females. Psychological Medicine, 1-7. Scientific American. heavy Cannabis Use Linked to Schizophrenia.

The ABCD Study, Adolescent Brain Cognitive Development, is the largest long-term study of brain development and child health in the United State. The study includes 21 research sites across the United States who invited 11,878 children ages 9-10 to join the study and follow through young adulthood. This study used the ABCD data on 4361 children age 8.9- to 11-year-old and found that offspring psychosis increased with the mother continued cannabis after she knew she was pregnant. Fine JD et al. Association of Prenatal Cannabis With Psychosis Proneness Among Children in the Adolescent Brain Cognition Development (ABCD) Study. JAMA Psychiatry. 2019;76(7):762-764.

This study compared 901 adult patients with first episode of psychosis across 11 sites with 1237 population controls and found that daily cannabis use was associated with increased odds of psychotic disorder compared with never users, increasing to nearly 5 times increased odds for daily use of high potency types of cannabis. Di Forti M et al. The contribution of cannabis use to variation in the incidence of psychotic disorders across Europe (EU-GEI): a multicenter case control study . Lancet Psychiatry. 2019;6(5):427-436. doi: 10.1016/S2215-0366(19)30048-3.

  • The study followed 3,720 Canadian students ages 13 to 16 and found that psychosis symptoms at age 15 had a statistically significant positive association with cannabis use at age 16. Bourque J, Afzali M, & Conrod P. Association of Cannabis Use With Adolescent Psychotic Symptoms. JAMA Psychiatry. 2018;75(8):864–866. https://doi.org/10.1001/jamapsychiatry.2018.1330 * This study evaluated 30 studies of healthy controls and ultra-high-risk (UHR) showed that UHR cannabis users had higher rates than nonusers of positive psychotic symptoms. Hasin DS. US Epidemiology of Cannabis Use and Associated Problems. Neuropsychopharmacology. 2018;43(1):195–212. doi:10.1038/npp.2017.198 * For this study, a systematic review was conducted of studies that investigated the association between cannabis consumption and psychosis. They included 18 studies and 66,816 individuals. The study found that higher levels of cannabis use increased the risk of psychotic outcomes and confirmed a dose-response relationship between the level of use and the risk for psychosis. Marconi A, Di Forti M, Lewis C, Murray R and Vassos E. Meta-analysis of the Association Between the Level of Cannabis Use and Risk of Psychosis. Schizophrenia Bulletin. 2017; 42(5):1262–1269. https://doi.org/10.1093/schbul/sbw003 - This publication reviewed 35 studies from 4804 references and revealed an increase in risk of psychosis of about 40% in participants who had ever used cannabis, and a 50-200% increase in risk for participants who used most heavily. Moore, T., Zammit, S., Lingford-Hughes, A., & Barnes, T. Cannabis use and risk of psychotic or affective mental health outcomes: a systematic review. The Lancet. 2007; 370(9584), 319–328. https://doi.org/10.1016/S0140-6736(07)61162-3

Prospective epidemiological studies have consistently demonstrated that cannabis use is associated with an increased subsequent risk of both psychotic symptoms and schizophrenia-like psychosis. Early onset of use, daily use of high potency cannabis, and synthetic cannabinoids carry the greatest risk. Functional MRI studies have linked the psychomimetic and cognitive effects of THC on areas of the brain implicated in psychosis. Murray RM et al. Cannabis-associated psychosis: Neural substrate and clinical impact. Neuropyschopharmacology. 2017;124:89-104. doi: 10.1016/j.neuropharm.2017.06.018

10 studies included 7390 patients age 12 – 65 showed an dose response association between use frequency and risk of psychosis. Weekly or more frequency of cannabis use showed higher risk. Robinson, T., Ali, M., Easterbrook, B., Hall, W., Jutras-Aswad, D., & Fischer, B. (2022). Risk-thresholds for the association between frequency of cannabis use and the development of psychosis: A systematic review and meta-analysis. Psychological Medicine

This cross-sectional analysis of 11,489 children age 9 – 11 from 22 sites across the United States between 2016 and 2018 showed increased risk of psychosis and psychopathology in children whose mothers used cannabis while pregnant. This was part of the ABCD longitudinal study. Paul SE, Hatoum AS, Fine JD, et al. Associations Between Prenatal Cannabis Exposure and Childhood Outcomes: Results From the ABCD Study. JAMA Psychiatry. 2021;78(1):64–76. doi:10.1001/jamapsychiatry.2020.2902

The 2017 National Inpatient Sample database found 129,070 hospital discharged for psychosis associated with cannabis use. There was a significant correlation between the cannabis legality score and proportion of psychosis associated with cannabis. Lauren V. Moran, Erica S. Tsang, Dost Ongur, John Hsu, May Y. Choi, Geographical variation in hospitalization for psychosis associated with cannabis use and cannabis legalization in the United States: Submit to: Psychiatry Research, Psychiatry Research,Volume 308,2022,114387,ISSN 0165-1781.

PTSD

  • The Clinical Practice Guideline for Management of PTSD and Acute Stress Disorder includes 34 recommendations. The CPG recommends against the use of benzodiazepines, cannabis, or cannabis-derived products. Providers are encourage to use this guide line to support evidence based, patient centered care and shared decision making to optimize individuals health outcomes and quality of life. Paula P. Schnurr, Jessica L. Hamblen, Jonathan Wolf, et al. The Management of Posttraumatic Stress Disorder and Acute Stress Disorder: Synopsis of the 2023 U.S. Department of Veterans Affairs and U.S. Department of Defense Clinical Practice Guideline. Ann Intern Med.2024;177:363-374. [Epub 27 February 2024].doi: 10.7326/M23-2757

  • From 1992 – 2011, 2276 veterans with PTSD were admitted to specialized VA treatment programs. At 4 months after discharge from the program subjects who started using marijuana had increased PTSD symptoms at a scale of +0.34, while those who stopped marijuana had a decrease of symptoms at a scale of -0.18. Initiating marijuana use after treatment was associated with worse PTSD symptoms, more violent behavior, and alcohol use. The authors concluded that marijuana appears to worsen PTSD symptoms and nullify the benefits of specialized intensive treatment. Cessation or prevention is an important goal of treatment. Wilkinson ST, Stefanovics E, Rosenheck RA. Marijuana use is associated with worse outcomes in symptom severity and violent behavior in patients with posttraumatic stress disorder. J Clin Psychiatry. 2015 Sep;76(9):1174-80. doi: 10.4088/JCP.14m09475. PMID: * 790 US Veterans completed a study on PTSD symptoms, substance use and marijuana use. Participants who had PTSD symptoms were more likely to be using marijuana and synthetic cannabis in their lifetimes and in the past month. Those with PTSD symptoms and marijuana use where more likely to expect marijuana to assist with relaxation and tension reduction. Grant S, Pedersen ER, Neighbors C. Associations of Posttraumatic Stress Disorder Symptoms With Marijuana and Synthetic Cannabis Use Among Young Adult U.S. Veterans: A Pilot Investigation. J Stud Alcohol Drugs. 2016 May;77(3):509-14. doi: 10.15288/jsad.201 + In a study of 200 men and women with chronic PTSD, individual who were using cannabis or other drugs were found to have a higher risk for not completing PTSD treatment and had prolonged cycle of PTSD and substance use. Bedard-Gilligan M, Garcia N, Zoellner LA, Feeny NC. Alcohol, cannabis, and other drug use: Engagement and outcome in PTSD treatment. Psychol Addict Behav. 2018 May;32(3):277-288. doi: 10.1037/adb0000355. Epub 2018 Mar 29. PMID: 29595297.

Cannabis Update 2025: Research on Depression, Anxiety, PTSD (Psychiatry Podcast, 2025) reports no improvement in PTSD symptoms. Cannabis use and trauma-focused treatment for co-occurring disorders (ScienceDirect, 2025) shows larger PTSD reductions but lower attendance. Cannabis Use and PTSD Among Veterans (VA, 2025) suggests harms with long-term use. Proceedings of the 2024 Cannabis Clinical Outcomes Research (PMC, 2025) notes cannabis use in PTSD with mixed outcomes. Cannabis Use Characteristics and PTSD-Related Outcomes (Journal of Veterans Studies, 2025) reports improvements in sleep but increased risks.

Public Health Several large prospective studies have followed teens through young adulthood, during the age of risk for using marijuana and for developing psychosis, in order to address the question of which behavior comes first. Out of five studies, one found a bidirectional effect and four determined that marijuana use significantly increased risk for subsequent psychosis, not vice-versa. * This study followed 6354 kids from age 15-16 until age 30. The authors concluded that the risk of developing psychosis was increased in individuals who tried cannabis 5 times or move. This increased risk was considered significant and adjusted for other risks such as parental psychosis, substance use, and more. "Mustonen A, Niemelä S, Nordström T, Murray GK, Mäki P, Jääskeläinen E, Miettunen J. Adolescent cannabis use, baseline prodromal symptoms and the risk of psychosis. Br J Psychiatry. 2018 Apr;212(4):227-233. doi: 10.1192/bjp.2017.52. PMID: 29557758. + The study followed 3,720 Canadian students ages 13 to 16 and found that psychosis symptoms at age 15 had a statistically significant positive association with cannabis use at age 16. Bourque J, Afzali M, & Conrod P. Association of Cannabis Use With Adolescent Psychotic Symptoms. JAMA Psychiatry. 2018;75(8):864–866. * This publication is a meta-analysis that evaluated 30 different studies of healthy controls and people at ultra-high-risk for psychosis (UHR), and showed that UHR cannabis users had higher rates than nonusers of positive psychotic symptoms. Carney R. et al. Cannabis use and symptom severity in individuals at high risk for psychosis: a meta-analysis. * For this study, a systematic review was conducted of studies that investigated the association between cannabis consumption and psychosis. They included 18 studies and 66,816 individuals. The study found that higher levels of cannabis use increased the risk of psychotic outcomes by an odd ratio of 3.9 and confirmed a dose-response relationship between the level of use and the risk for psychosis. Marconi A, Di Forti M, Lewis C, Murray R and Vassos E. Meta-analysis of the Association Between the Level of Cannabis Use and Risk of Psychosis. Schizophrenia Bulletin. 2017; 42(5):1262–1269. * This publication reviewed 35 studies from 4804 references and revealed an increase in risk of psychosis of about 40% in participants who had ever used cannabis, and a 50-200% increase in risk for participants who used most heavily. The studies analyzed included the lower potency marijuana from previous years. Moore, T., Zammit, S., Lingford-Hughes, A., & Barnes, T. Cannabis use and risk of psychotic or affective mental health outcomes: a systematic review. The Lancet. 2007; 370(9584), 319–328. - 10 studies included 7390 patients age 12 – 65 showed an dose response association between use frequency and risk of psychosis. Weekly or more frequency of cannabis use showed higher risk Robinson, T., Ali, M., Easterbrook, B., Hall, W., Jutras-Aswad, D., & Fischer, B. (2022). Risk-thresholds for the association between frequency of cannabis use and the development of psychosis: A systematic review and meta-analysis. Psychological Medicine

  • This study is based on a study from Finland in 18,478 patients. Cannabis induced psychosis resulted in 46% 8-year risk of schizophrenia spectrum diagnosis. For amphetamine induced psychosis the risk was 30%. Niemi-Pynttari JA, et al. Substance Induced Psychosis Converting into Schizophrenia: A Register Based Study of 18,478 Finnish Inpatient Cases. J Clin Psychiatry 2013; 74(1):394-e99.
  • This study compared 901 adult patients with first episode of psychosis across 11 sites with 1237 population controls and found that daily cannabis use was associated with increased odds of psychotic disorder compared with never users, increasing to nearly 5 times increased odds for daily use of high potency types of cannabis. The percent of cases of psychosis in each site would have been lower if cannabis was avoided. Di Forti M et al. The contribution of cannabis use to variation in the incidence of psychotic disorders across Europe (EU-GEI): a multicenter case control study . Lancet Psychiatry. 2019;6(5):427-436. doi: 10.1016/S2215-0366(19)30048-3.
  • Prospective epidemiological studies have consistently demonstrated that cannabis use is associated with an increased subsequent risk of both psychotic symptoms and schizophrenia-like psychosis. Early onset of use, daily use of high potency cannabis, and synthetic cannabinoids carry the greatest risk. Functional MRI studies have linked the psychomimetic and cognitive effects of THC on areas of the brain implicated in psychosis. Murray RM et al. Cannabis-associated psychosis: Neural substrate and clinical impact. Neuropyschopharmacology. 2017;124:89-104. doi: 10.1016/j.neuropharm.2017.06.018
  • The ABCD Study, Adolescent Brain Cognitive Development, is the largest long-term study of brain development and child health in the United State. The study includes 21 research sites across the United States who invited 11,878 children ages 9-10 to join the study and follow through young adulthood. This study used the ABCD data on 4361 children age 8.9- to 11-year-old and found that offspring psychosis increased when the mother continued to use cannabis after she knew she was pregnant. Fine JD et al. Association of Prenatal Cannabis With Psychosis Proneness Among Children in the Adolescent Brain Cognition Development (ABCD) Study. JAMA Psychiatry. 2019;76(7):762-764.

The Bradford Hill elements of causation illustrate a causal relationship between the use of marijuana and the development of psychosis. As seen for other agents associated with disease outcomes, the Bradford Hill analysis has been essential to our understanding. There was a time when physicians did not realize that smoking tobacco and developing lung cancer were related in a causal sense, and applying the Bradford Hill analysis to the epidemiology of lung cancer revealed the causal association. You will find the corresponding analysis for marijuana and psychosis here.

  • The 2017 National Inpatient Sample database found 129,070 hospital discharged for psychosis associated with cannabis use. There was a significant correlation between the cannabis legality score and proportion of psychosis associated with cannabis. Lauren V. Moran, Erica S. Tsang, Dost Ongur, John Hsu, May Y. Choi, Geographical variation in hospitalization for psychosis associated with cannabis use and cannabis legalization in the United States: Submit to: Psychiatry Research, Psychiatry Research,Volume 308,2022,114387,ISSN 0165-1781.

The World Federation of Societies of Biological Psychiatry Task Force reviewed the literature of liberalization of cannabis laws and the risk of psychosis. The concluded that delaying or eliminating cannabis exposure can decrease the rate of psychosis related to cannabis. Deepak CJ, DiFort M, et al. Consensus paper of the WFSBP task force on cannabis, cannabinoids and psychosis, The World Journal of Biological Psychiatry, 2022.

Increased marijuana poisoning in children follows increased availability and increased potency. Visit any cannabis store in person or on-line and you will find concentrates at over 90% THC. High potency THC can behave like a hard drug, like methamphetamine. Dosing in children is a major concern. One gummy of 10 mg THC for an adult can cause psychosis. For a child it can cause altered mental status, encephalopathy, or delirium. Roneet Lev, MD FACEP. Marijuana Candy: Poisoning and Lack of Protection for Children February 1, 2023

  • The medical and scientific community have set criteria of what constitutes a medicine. We now have a system where politicians not doctors can decide what a medicine is. Standard Criteria for marijuana to be considered a medicine include: - The chemistry of the drug must be known and reproducible - Adequate safety studies much have been done - Adequate and well controlled studies must have proven the efficacy of the drug - The drug must be accepted by qualified experts - The scientific evidence must be widely available These criteria have not been met of the marijuana plant or the numerous cannabis-based products. Voth EA. And Schwartz RS. Medical Applications of Delta-9-Tetrahydrocannabinol and Marijuana. Annals of Internal Medicine. Vol 126; No 10, 1997. - Bypassing the usual safety and efficacy process of the FDA is a dangerous and unnecessary precedent which widely enhances the availability and acceptance of marijuana. Voth, EA. A Peek into Pandora’s Box: The Medical Excuse Marijuana Controversy. Journal of Addictive Diseases. Vol 22, No 4, 2003.

Cannabis is the most widely illegal drug in Ireland with 8% of adults reporting some use in the past year and the most likely substance to cause people under the age of 25 to seek addiction treatment. The authors warn of the slippery slope where politicians bypass the Health Product Regulatory Authority in determining what is and what is not a medicine. Despite the lack of scientific evidence for efficacy, chronic pain is by far the most common reason for dispensing of cannabis despite the lack of scientific evidence. Smyth, B.P., Cannon, M. Cannabis and public health—a need to reclaim the narrative. Ir J Med Sci (2021). https://doi.org/10.1007/s11845-021-02570-x

Cannabis use is increasing among young adults, but its effects on cardiovascular health are poorly understood. We aimed to assess the association between recent cannabis use and history of myocardial infarction (MI) in young adults (aged 18–44 yr). Karim S. Ladha, Nikhil Mistry, Duminda N. Wijeysundera, Hance Clarke, Subodh Verma, Gregory M.T. Hare and C. David Mazer CMAJ September 07, 2021 193 (35) E1377-E1384; DOI: https://doi.org/10.1503/cmaj.202392

Cannabis Use in Adolescents (PMC, 2025) notes public health risks like declined perceived harm. Cannabis Facts and Stats (CDC, 2025) covers use, ED visits, misuse. 2025 Cannabis Health Statistics Report (CT.gov, 2025) shows over half perceive moderate risk. Cannabis: Health, Research and Regulatory Considerations (AAFP, 2025) discusses pollution harms. Largest Study Ever Done on Cannabis and Brain Function (CU Anschutz, 2025) highlights cognitive harms.

Pulmonary Health / Asthma / COPD

  • This 40-year study found that heavy cannabis smoking was significantly associated with more than a twofold risk of developing lung cancer. Callaghan R, Allebeck P, and Sidorchuk A. Marijuana use and risk of lung cancer: a 40-year cohort study. Cancer Causes & Control. 2013; 24(10):1811–1820.

  • This study reviewed chest CT examinations on 56 marijuana smokers, 57 nonsmoker controls, and 33 tobacco only smokers. Marijuana smokers had a higher rate of emphysema 75%, compared to nonsmokers 5%, and tobacco smokers 67%. Airway inflammation and emphysema were more common in marijuana smokers. Murtha. L et al. Chest CT Findings in Marijuana Smokers. Radiological Society of North America. Nov 2022.

In a survey of 5410 adults living in Oklahoma, 42% reported past 30-day second-hand cannabis smoke exposure. Respiratory symptoms were highest among those reporting past 30 days second hand cannabis smoke exposure and past 30-day cannabis use. Those exposed were more socially and economically vulnerable. Cohn AM, Zaring-Hinkle B, Catino JD, Ehlke SJ, Ware K, Alexander A, Smith MA, Jewell-Fleming S, Queimado L, Kendzor DE. Secondhand cannabis smoke exposure and respiratory symptoms among adults living in a state with legalized medical cannabis with limited

Inhaling Cannabis May Greatly Increase Your Risk of Lung Disease (UCSF, 2025) associates smoking with increased asthma risk. Inhaled Cannabis, Asthma, and Chronic Obstructive Pulmonary Disease (Springer, 2025) links to COPD. Inhaled Cannabis, Asthma, and COPD (PubMed, 2025) associates with asthma and COPD after adjusting for tobacco. Effects of Inhaled Tobacco and Cannabis Co-Use on Respiratory Health (ATS, 2025) prioritizes harms. Inhaled Cannabis Linked to Risk for Asthma, COPD (Drugs.com, 2025).

Schizophrenia Schizophrenia is a serious mental health disorder of misinterpretation of reality. Symptoms include hallucinations, delusions, and disordered thinking and behavior. Psychosis (see different library section) is a symptom to being out of touch with reality such as hallucinations, delusions, and disordered thinking. Schizophrenia is a DSM V disorder, while psychosis is a symptom not a disease. * A study in Demark studied 7,186,834 individuals 16 year and older from 1972 to 2016 and evaluated all people who required psychiatric service for cannabis use or schizophrenia. Cannabis use disorder increased the risk of developing schizophrenia later by 5-fold. This means the adjusted hazard ratio for developing schizophrenia is 5. The population attributable risk factor (PARF) explains the risk of a disease caused by an offending agent. For example, if no one smoke tobacco we would prevent 90% of lung cancer cases. The PARF for schizophrenia caused by cannabis increased from 2% in the 1970s and 1980s to 8% in 2016. This is a 7-fold increase in schizophrenia attributed to cannabis over time. The author states that “Cannabis is not a safe drug.” Hjorthøj C, Posselt CM, Nordentoft M. Development Over Time of the Population-Attributable Risk Fraction for Cannabis Use Disorder in Schizophrenia in Denmark. JAMA Psychiatry. Published online July 21, 2021. doi:10.1001/jamapsychiatry.2021.1471

The study population from the Danish Civil Registration System included all persons who received a diagnosis of substance-induced psychosis between 1994 and 2014 (N56,788). Cannabis induced psychosis had the highest rate of conversion to schizophrenia or bipolar disorder at 47.7% compared to opioids, cocaine, hallucinogens, alcohol. sedatives or amphetamines. Starzer, MSK, et al. Rates and Predictors of Conversion to Schizophrenia or Bipolar Disorder Following Substance-Induced Psychosis. Am J Psychiatry.

Seizures

  • Synthetic marijuana, also known as “Spice” is a chemical produced in a lab with similar structure to THC. Spice does not show up on drug screens. It is a well established cause of seizures. de Havenon A, Chin B, Thomas KC, Afra P. The secret "spice": an undetectable toxic cause of seizure. Neurohospitalist. 2011;1(4):182-186. doi:10.1177/1941874411417977 - Natural cannabinoid delta-9-THC 10mg/kg and synthetic cannabinoid JWH-018 (spice) triggered electrographic seizures in mice. Malyshevskaya, O., Aritake, K., Kaushik, M.K. et al. Natural (∆ 9-THC) and synthetic (JWH-018) cannabinoids induce seizures by acting through the cannabinoid CB 1 receptor. Sci Rep 7, 10516 (2017). https://doi.org/10.1038/s41598-017-10447-2

  • The Bradford Hill Criteria is a methodology used to prove causation rather than association. It was used for proving tobacco caused lung and heart damage. The Bradford Hill criteria was used to show that delta-8 THC have seizure causing effects. Kaczor EE, Greene K, Zacharia J, Tormoehlen L, Neavyn M, Carreiro S. The Potential Proconvulsant Effects of Cannabis: a Scoping Review. J Med Toxicol. 2022 Mar 29. doi: 10.1007/s13181-022-00886-3. Epub ahead of print. Erratum in: J Med Toxicol. 2022 Apr 2

Suicide Libby Stuyt, MD an addiction psychiatrist in Colorado and IASIC physician advisory council member published an Op-ED reviewing data that causes alarm. Stuyt reviewed data from large patient studies in the Veteran’s population, Colorado population, and youth studies. Libby Stuyt, MD. Op-Ed: Are Marijuana Use and Suicide Linked? — A review of the data show there's cause for alarm MedPage Today April 23, 2021

  • In this cross-sectional study of 68,263 adolescents, non-disordered cannabis use (NDCU) and cannabis use disorder (CUD were both significantly associated with adverse psychosocial events in a stepwise gradient manner. This included major depression, suicidal ideation, slower thoughts, difficulty concentrating, truancy, fighting, and aggression. Adolescent who met the diagnosis for cannabis use disorder or used the drug recreationally had a 2 - 4 times higher prevalence of depression and suicidal ideation that those who didn't sue cannabis. R.S. Sultan, et al. Nondisorderd Cannabis Use Among US Adolescents. JAMA Netw Open, 2023. * This study compared incidence of suicide attempts in young adults age 18 – 45. Cannabis Use Disorder with Underlying major depression had the highest incidence of suicide attempt. Cannabis Use Disorder and Daily Cannabis use increase incidence of suicide attempt both in people with and without major depressive disorder. Females had higher incidence than males in all categories. Han et al, awaiting publication. Dr. Nora Volkow, NIDA slide SAM Summit 2022. - This study examined NSDUH (National Surveys on Drug Use and Health) data from 281,650 adults ages 18 – 34 between January 2008 and December 2019 and noted an increase of 40% to 60% in suicidal ideation, plan and attempt associated with cannabis use and major depression. Han B, Compton WM, Einstein EB, Volkow ND. Associations of Suicidality Trends With Cannabis Use as a Function of Sex and Depression Status. JAMA Netw Open. 2021;4(6):e2113025. doi:10.1001/jamanetworkopen.2021.13025 * This study was conducted from a registry of 13,986 twins from Australia. A monozygotic (Identical) twin who use cannabis frequently was more likely to report suicidal ideations compare to their identical twin who used cannabis less frequently, even after adjustment for other variants. There the increased likelihood of suicidal ideation in frequent cannabis users cannot be solely attribute to common predisposing factors. Agrawal A, Nelson EC, Bucholz KK, Tillman R, Grucza RA, Statham DJ, Madden PA, Martin NG, Heath AC, Lynskey MT. Major depressive disorder, suicidal thoughts and behaviours, and cannabis involvement in discordant twins: a retrospective cohort study. Lancet - This study involved 6445 individuals who received treatment for cannabis use disorder in Denmark and determined a higher mortality rate than the general population. The most common cause of death was accidents. Suicide occurred 5 times more frequently than a control population and homicides occurrent 4 times as often. Arendt M, Munk-Jørgensen P, Sher L, Jensen SO. Mortality following treatment for cannabis use disorders: predictors and causes. J Subst Abuse Treat. 2013 Apr;44(4):400-6. doi: 10.1016/j.jsat.2012.09.007. Epub 2012 Nov 2. PMID: 23122774. * This study evaluated 743 adolescents for psychopathology. They compared adolescents with suicidal ideations to a control population. This study showed that any use of cannabis in early adolescent period is a strong independent predictor of attempted suicide in young adulthood. Clarke MC, Coughlan H, Harley M, et al. The impact of adolescent cannabis use, mood disorder and lack of education on attempted suicide in young adulthood. World Psychiatry. 2014;13(3):322-323. doi:10.1002/wps.20170 * This study included long running longitudinal data from Australia to New Zealand that followed 3765 participants from age 17 until 30. They recorded clear and consistent associations and dose-response relations between frequent adolescent cannabis use and all adverse young adult outcomes including suicide attempt. Silins E, Horwood LJ, Patton GC, Fergusson DM, Olsson CA, Hutchinson DM, Spry E, Toumbourou JW, Degenhardt L, Swift W, Coffey C, Tait RJ, Letcher P, Copeland J, Mattick RP; Cannabis Cohorts Research Consortium. Young adult sequelae of adolescent cannabis
  • Completed suicides in Colorado have increased steadily from 2004 to 2018. Marijuana was present in 12.8% of all 14,229 suicides. For all ages, alcohol was the leading cause of drug found on death at 35.5%. However, for ages 10 – 19, marijuana was the leading drug found in 19.8% or 943 completed suicides, surpassing alcohol at 12.8%. The Colorado Center for Health and Environmental Data, Department of Public Health and Environment.

269 adolescent suicide cases in Colorado were analyzed. Marijuana was found in 16.1% of adolescent suicide cases (age 10-19) compared with 6.9% of adults. Marijuana was found more than alcohol (12.7%) on toxicology results. Jamison E, Bui AG, Herndon K, Bol K. Adolescent suicide in Colorado, 2008-2012. 2014 Nov;94:1-8. https://www.colorado.gov/pacific/sites/default/files/CHED_VS_Health-Watch-No-94-Adolescent-Suicide-in-Colorado-2008-2012_0817.pdf

  • This cohort study evaluated health insurance claims data from 75,395,344 beneficiaries between 2003 and 2017, finding that rates of self harm injuries among males younger than 40 years increased more in states legalizing recreational cannabis dispensaries compared to states without legalization. Matthay, EC. Et al. Evaluation of State Cannabis Laws and Rates of Self-harm and Assault. JAMA Network Open. March 2021.

Associations between cannabis use frequency and suicidal thoughts (ScienceDirect, 2025) notes increased risk independent of depression. Racial and Ethnic Differences in Suicide Mortality (PubMed, 2025). Cannabis use associated with increased suicide risk (AddictionPolicy, 2025) even controlling for depression. Evidence Mounting That Connects Cannabis to Youth Depression (PsychiatryOnline, 2024) fuels suicide. Marijuana Dependence Linked to Higher Risk of Death (NYTimes, 2025) links to 10x suicide risk.

Vaping

  • This study of 14,798 adolescents age 12 -17 showed that respiratory symptoms such as wheezing was 2 times higher among those who used cannabis in vaping devises (ENDS – electronic nicotine delivery systems), more than those who used either e-cigarettes or regular cigarettes. Boyd CJ, et al. Cannabis, Vaping, and Respiratory Symptoms in a Probability Sample of U.S. Youth. J of Adolescent Health. March 2021.

  • Pollution levels as fine particulate matter in the air and how long they persistent was compared with marijuana joint, the bong with its bowl, the glass pipe, electronic vaping pen, and a Marlboro cigarette inn 60 controlled experiments. Cannabis joints were the most polluting – 3.5 times that of a Marlboro. The emission rate for a cannabis bong was 67% that of a joint; the glass pipe’s emission rate was 54% of the joint, and the vaping pen’s emission rate was 44% of the joint, as polluting as a cigarette, but hung around longer. Wayne R. Ott, Tongke Zhao, Kai-Chung Cheng, Lance A. Wallace, Lynn M. Hildemann, Measuring indoor fine particle concentrations, emission rates, and decay rates from cannabis use in a residence, Atmospheric Environment: X, Volume 10, 2021,100106,ISSN 2590-1621,https://doi.org/10.1016/j.aeaoa.2021.100106.

The approval of vaping products to the American market has been a public health disaster. This paper quantifies the balance of health benefits and harms associated with e-cigarette use at the population level. They use simulation models using census counts, national health and tobacco use surveys, and published literature. They calculate the expected years of life gained or lost from the impact of e-cigarette use on smoking cessation and current smokers and transition to long-term cigarette smoking among never smokers for the 2014 US population. The model estimated 2,070 additional current cigarette smoking adults aged 25-69 would quit smoking in 2015 and remain continually abstinent from smoking for > 7 years through use of e-cigarettes in 2014. The model also estimated 168,000 additional never-cigarette smoking adolescents aged 12-17 and young adults aged 18-29 would initiate cigarette smoking in 2015. Overall, the model estimated that e-cigarette use in 2014 would lead to 1,510,000 years of life lost. The authors conclude that e-cigarette use currently represents more population-level harm than benefit. Of note the research uses optimistic assumption about success of vaping for tobacco cessation, using data from Europe where cigarette use is more common. Soneji SS, Sung H-Y, Primack BA, Pierce JP, Sargent JD (2018) Quantifying population-level health benefits and harms of e-cigarette use in the United States. PLoS ONE 13(3): e0193328.

Sound the Alarm: Youth Vaping can Harm (HHS.gov, 2025) notes oral effects like gum disease, impaired healing. Vaping cannabinoid mixtures produces a chemical that destroys lungs (MedicalXpress, 2025) with toxic byproducts. Vaping and harm in young people (Tobacco Control, 2025) associates with pneumonia, lower sperm, dizziness. Cannabis concentrate vaping chemistry (PMC, 2025) notes greater risk of severe CUD. Vaping & Lung Health: Is It Still a Concern in 2025? (Lyracore, 2025) links to inflammation, immune impairment.

Violence This study reviewed 113,454 participants aged 18-34 between 2015-2019 in the NSDUH data. Past year violent behavior was highest among males with daily cannabis use with CUD, 3.1%. Males with daily cannabis without CUD had violence at prevalence of 2.9%. Males without cannabis use have violence at 1.7%. Violent behavior in females with cannabis use was higher than those without cannabis use. Volkow ND, Compton WM, Blanco C, Einstein EB, Han B. Associations of cannabis use, use frequency, and cannabis use disorder with violent behavior among young adults in the United States. Int J Drug Policy. 2024

  • Consistent marijuana use was related to an increased risk of intimate partner violence in a longitudinal study of 9,421 subjects ages 15 – 26. Consistent marijuana use, particularly consistent use throughout adolescence, is associated with perpetration or both perpetration of and victimization by intimate partner violence in early adulthood. Marijuana use should be considered as a target of early intimate partner violence intervention and treatment programming. Reingle JM, et al. The Relationship Between Marijuana Use and Intimate Partner Violence in a Nationally Representative, Longitudinal Sample. Journal of Interpersonal Violence. 2012;27(8) 1562-1578. DOI:10.1177/0886260511425787.
  • 296,815 adolescents and young adults were included in 30 studied. Evidence showed that the risk of violence was higher for persistent heavy users compared with past-year users and lifetime users. The results showed a significant association of cannabis use and physical violence even with adjustment for socioeconomics and other substance use. Dellazizzo L, Potvin S, Dou BY, Beaudoin M, Luigi M, Giguère CÉ, Dumais A. Association Between the Use of Cannabis and Physical Violence in Youths: A Meta-Analytical Investigation. Am J Psychiatry. 2020 Jul 1;177(7):619-626. doi: 10.1176/appi.ajp.2020.191

Withdrawal

  • Symptoms of marijuana withdrawal include: anxiety, diminished appetite, mood changes, irritability, sleep difficulties, including insomnia, headaches, loss of focus, cravings for marijuana, sweating, including cold sweats, chills, increased feelings of depression, stomach problems. These symptoms can range from mild to more severe, and they vary from person to person. These symptoms may not be severe or dangerous, but they can be unpleasant. The longer someone uses marijuana, the more likely they are to experience withdrawal symptoms. Hasin DS. US Epidemiology of Cannabis Use and Associated Problems. Neuropsychopharmacology. 2018;43(1):195-212.

Cannabis Withdrawal and Psychiatric Intensive Care (JAMA, 2025) notes violence during assessments. Cannabis and psychopathology (PMC, 2025) reports females have increased rate and severity of withdrawal. Cannabis Update 2025 (Psychiatry Podcast, 2025). Psychosis associated with cannabis withdrawal (Cambridge, 2024) links to acute psychosis. The role of cannabis (Laboratoire de recherche, 2025) focuses on treatments for withdrawal.