Doctors Warn: Cannabis Can Cause Serious Health Hazards

IASIC, the International Academy on the Science and Impact of Cannabis, is a medical organization of doctors who educate on marijuana based on the scientific and medical literature. IASIC is a non-partisan and non-political group created to facilitate informed decisions when considering cannabis policy and law.

Visit the IASIC Library to few medical literature on the harms of cannabis translated for public understanding.

It is our conclusion, based on review of the scientific evidence, that public health effects of high potency cannabis are harmful.  These growing negative impacts further strain health care and addiction treatment resources to an extent that far surpasses taxation revenues.

Evidence: Thousands of peer-reviewed medical articles have been published on the harms of cannabis and marijuana. Reviews of medical benefits of cannabis published in highly ranked journals reveal only limited benefits for rare conditions, and generally do not consider long-term consequences.

Emergency Department (ED) Visits: The San Diego Marijuana Prevention Initiative report reflects 29 emergency visits a day for cannabis-related illnesses.1 In a large urban hospital in Colorado cannabis-related ED visits more than tripled from 2012 to 2016.2 A 2017 study showed that in adolescent cannabis ED visits, approximately 71% were given a psychiatric diagnosis.3

Psychosis: There is strong evidence for severe mental health problems triggered by cannabis. Multiple studies link regular cannabis use to an estimated doubling of the risk of a psychotic illness; the resulting psychosis can become permanent and a lifelong disability.4 Violent behavior as a result of cannabis-induced paranoia and psychosis is a growing concern.5 A 2019 study from Lancet Psychiatry found that if high-potency cannabis were no longer available, 12.2% of cases of first-episode psychosis could be prevented; in some places avoiding heavy cannabis use could prevent up to 50% of psychosis cases.6

Suicide: There is significant evidence linking cannabis use and suicide, especially in teens and young adults. A 2019 review of multiple publications found that adolescent cannabis use was associated with increased depression in young adulthood and a tripling of the risk of a suicide attempt.7 Marijuana is the most prevalent substance found in completed teen suicide in the state of Colorado.8 Evidence suggests that self-harm increases by 46% in young men in states that commercialize cannabis.9

Brain Development: It is well established that brain development starts in utero and continues until the mid 20s. The use of any addicting drug during this time period increases the likelihood of addiction.10 Heavy cannabis use has shown visible negative alterations in both brain structure and function.11, 12 The ABCD study on adolescent brain cognitive development found that psychosis increased in offspring when the mother continued cannabis after she was aware she was pregnant.13 The study continues to track the health of thousands of kids over time.

Neonatal Exposure: Cannabis use is not recommended in pregnancy and is associated with low birth weight14 and future cognitive and emotional problems in children.15 Despite these known risks, a recent investigation into regulated cannabis dispensaries in Colorado found that employees when asked, recommended cannabis for pregnancy-associated morning sickness 69% of the time and usually did not recommend speaking to the woman’s physician first.16

Opioid Crisis: Cannabis use has been shown to increase the likelihood of opioid use disorder and opioid misuse.17, 18 In the United States, 81,000 drug overdose deaths in 2020 represent a 12.5% increase from the year before. Medical marijuana states have 23% higher opioid overdose deaths than states without medical marijuana.19

In 2021, both the International Association for the Study of Pain and the Australian and New Zealand College of Anesthetists, Faculty of Pain Medicine both “do not recommend the use of cannabinoids for chronic non-cancer pain” and there is a “lack of high-quality evidence for the use of cannabinoids in chronic non-cancer pain”.20, 21

Traffic Fatalities: The risk of car collisions increases two-fold after smoking cannabis.22 Traffic fatalities increased in the first four states to legalize recreational marijuana compared to states without legal marijuana.23

High Potency Use, Problematic and Youth Use: Higher cannabis shop density has been associated with a 6.8% increase in marijuana-related hospitalizations.24 Limiting the availability of high potency cannabis may be associated with decreased marijuana addiction and mental illness.25

Cannabis Hyperemesis Syndrome: CHS is now commonly recognized as presenting to EDs in long-term cannabis users. CHS is potentially fatal and associated with painful retching, vomiting, and abdominal pain.26

Conclusions: We recognize that there are many sides to the marijuana debate, and we call attention to the growing science on public health risk. Tobacco was promoted as relatively harmless before nicotine addiction became ubiquitous and the link to lung cancer was proven. The opioid industry marketed its drugs as non-addictive and safe in the early 1990s, and we are still paying the price. Let’s learn from our historical mistakes and not repeat them with marijuana. Drug addiction and death have increased during the COVID-19 pandemic. We urgently need smart public health policies that follow the science, prevent addiction, and decrease mental illness including psychosis, depression, and suicide.

IASIC, The International Association on Science and Impact of Cannabis, hopes lawmakers and voters will follow the science and promote public health.

1MPI Report Card. San Diego, 2021.

2Monte et al., Annals of Internal Medicine 2019.

3Wang et al., Journal of Adolescent Health 2018. j.jadohealth.2017.12.010

4Starzer et al., 2017 The American Journal of Psychiatry. appi.ajp.2017.17020223

5Moulin et al., 2018 Frontiers in Psychiatry (Forensic Psychiatry). fpsyt.2018.00294 fpsyt-09-00294.pdf

6Di Forti et al., Lancet Psychiatry 2019.

7Gobbi et al., JAMA Psychiatry 2019. doi: 10.1001/jamapsychiatry.2018.4500

8Colorado Violent Death Reporting System. 2016. Available at: https:// Story1?:embed=y&:showAppBanner=false&:showShareOptions=true&:display_count=no&:sho wVizHome=no#4. [Google Scholar]

9Humphreys et al., JAMA Network Open. 2021. doi: 10.1001/jamanetworkopen.2021.1955

10Winters KC. Drug Alcohol Depend. 2008.

11Manza et al., Molecular Psychitry. 2019.

12Comchong et al., Cerebral Cortex. 2017. doi: 10.1093/cercor/bhw015

13Fine et al., JAMA Psychiatry. 2019;76(7):762-764. doi: 10.1001/jamapsychiatry.2019.0076

14Crume et al., Journal of Pediatrics. 2018. Epub 2018 Mar 28. doi: 10.1016/ j.jpeds.2018.02.005.

15Goldschmidt et al., 2000 Neurotoxicology and Teratology 22(3):325-36 doi:10.1016/S0892-0362(00)00066-0 or Day et al., Psychol Med Epub 2014 Dec 23. doi: 10.1017/S0033291714002906.

16Dickson et al., Obstet Gynecol 2018 Jun;131(6):1031-1038. doi: 10.1097/ AOG.0000000000002619.

17Olfson et al., The American Journal of Psychiatry. 2017.

18Secades-Villa et al., Int J Drug Policy. 2015. February;26(2):135–142. doi: 10.1016/ j.drugpo.2014.07.011.

19Shover et al., 2019 Proc Natl Acad Sci U S A. 2019 Jun 25;116(26):12624-12626. doi: 10.1073/pnas.1903434116. Epub 2019 Jun 10.

20 International Association for the Study of Pain Presidential Task Force on Cannabis and Cannabinoid Analgesia position statement; doi: 10.1097/j.pain.0000000000002265

21 Recommendations from the Faculty of Pain Medicine, ANZCA;

22Hartman, et al., 2013 Clin Chem 2013 Mar;59(3):478-92. doi: 10.1373/clinchem.2012.194381.

23Kamer, et al., 2020. JAMA Internal Medicine. 2020;180(8):1119-1120. doi: 10.1001/ jamainternmed.2020.1769

24Mair, et al., 2015 Drug Alcohol Dependence doi: 10.1016/j.drugalcdep.2015.06.019

25Hines, et al., 2020. JAMA Psychiatry doi: 10.1001/jamapsychiatry.2020.1035

26Nourbakhsh, et al., 2019. J Forensic Sci 2019 Jan;64(1):270-274. https://

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