Cannabis and Psychosis

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“Psychosis is associated with more frequent and longer use of cannabis.” – Di Forti et al[1]

After alcohol, marijuana is the most used psychotropic drug in America. In 2018, more than 11.8 million young adults reported marijuana use in the past year.[2]  Marijuana (also known as cannabis, weed, pot, dope, or grass) is the most widely used illegal drug in the UK; however, in the United States, we have seen a widespread shift towards the legalization of this drug. So far, 15 U.S. states and Washington D.C. have legalized marijuana for adult recreational use, and 36 states permit medical use of the drug.[3]

Legalizing marijuana for medical and recreational use has bolstered an already widespread opinion that cannabis is a “soft drug,” that its effects are benign, and that it is almost a rite of passage for the young that is no more dangerous than taking your first sip of wine.

The National Institute on Drug Abuse reports that there is a significant gender discrepancy in America, as cannabis use is far more prevalent among young males than young females.[4]  The effects also vary between the sexes, as research shows that males display a greater cannabis-induced high while females’ spatial memory is more likely to be impaired.[5]   Men also use cannabis more frequently and in higher quantities and are more likely to use concentrated forms of administration such as blunts or vaporizers while women are more likely to use pipes. Studies also suggest that women are more likely than men to experience serious withdrawal symptoms such as nausea, paranoia, and anxiety.[6]

Cannabis use is especially common among young adults and adolescents and is increasing each year. A 2020 study from the National Institute on Drug Abuse showed that, in 2019, 11.8% of 8th graders reported regular marijuana use in the past year.  This grew to 28.8% of 10th graders and 35.7% of 12th graders.[7]

Often, teenagers justify their use of marijuana because of its use for medical purposes.  Laws for medical marijuana differ from state to state, and the legislation surrounding it can alter rather rapidly.  Children of any age can access medical marijuana if they have a qualifying condition in certain states.  However, to date, there is no evidence that medical marijuana is any safer than any other form of marijuana.

There have long been associations between cannabis use and the onset of schizophrenia, and this article will separate the marijuana myths from the facts and explore the connections between cannabis use and psychosis.

Cannabis Explained

Cannabis refers to a group of three plants with psychoactive properties: Cannabis sativa, indica, and ruderalis.  The harvesting and drying of the flowers create the form of the drug that is smoked or ingested.  The effects of cannabis vary depending on the type, the amount, and the person using it.

Some examples of the perceived “positive” effects of cannabis include:[8]

  • Feeling chilled out, blissful, relaxed, and happy
  • Laughing, or becoming more excitable or talkative
  • Hunger pangs (“the munchies”)
  • Altered mind states and mild hallucinations

While marijuana is widely considered to not be physically addictive, regular or heavy users or those who are more susceptible can become dependent and experience withdrawal symptoms such as nausea, insomnia, loss of appetite, irritability, sweating, and diarrhea.  If smoked with tobacco, users may also experience nicotine withdrawals.

Adverse consequences of Marijuana use include:[9]

  • Impaired short-term memory
  • Impaired cognitive functions, including attention, coordination, and judgment
  • Increased heart rate
  • Anxiety, paranoia
  • Dependence
  • Impaired respiratory function
  • Cardiovascular disease
  • Impairments in learning and memory
  • Risk of schizophrenia

Cannabis and the Risk of Psychosis

Generally, the adverse effects listed above are short-lasting and dissipate once the effects of the drug have worn off. However, some cannabis users will go on to develop long-lasting or even permanent psychosis.

Cannabis contains two active ingredients called cannabinoids: tetrahydrocannabinol (THC) and cannabidiol (CBD).  THC is responsible for the psychoactive effects, and the amount of THC in cannabis is considerably higher today than it was in the 1960s and 1970s, with rates that continue to escalate.  THC levels in cannabis have risen from 8.9% in 2008 to 17.1% in 2017, and the mean THC:CBD ratio also rose substantially, from 23 in 2008 to 104 in 2017.[10]

Psychosis is determined by a pattern of unusual thoughts or perceptions, hallucinations, and delusions (believing things that are not really true) and is thought to increase the risk of developing schizophrenia.[11]  It is important to note that cannabis use in adolescence is also associated with an increased risk of depression, anxiety, and suicidal ideation.[12]  Data from a study conducted in 2018 in Colorado demonstrated increased psychiatric emergency department (ED) visits from adolescents using cannabis and a fivefold higher prevalence of mental health diagnoses within those visits.[13]

It is clear that some people are more susceptible to the harmful effects of cannabis than others based on the following factors:.[14]

  • Medical History – If an individual has a predisposition to psychosis due to their personal or family history, then they will be at a greater risk of developing cannabis-induced psychosis. 
  • Age – Age is an important factor, as teenagers are deemed to be more at risk of developing psychosis than adults. This is either while they are still young or as adults if they starting using as teenagers.  
  • Genetic – A recently-identified gene, catechol-O-methyltransferase, may make a person more vulnerable to the effects of cannabis. Studies show that those with this gene may have a five times greater risk of exhibiting psychosis and developing schizophreniform disorder than those who do not have it.

Additionally, cannabis increases the risk of a relapse in people who already have schizophrenia, and it can worsen psychotic symptoms.[15]

Conclusion The rapid growth of the cannabis industry, legalization, medical use, and the onset of changes in public perceptions about the risks of cannabis have increased the popularity of this drug among today’s teenagers and young adults. It is imperative that further research is conducted to better understand the effects of cannabis and the associated risks of psychosis.  This information must be made publicly available to enable healthcare professionals and policymakers to make informed decisions about the risks of cannabis use and to allow our teenagers to make educated judgements.

If you are concerned about any issues discussed in this blog, please contact Heather R. Hayes & Associates – call 800-335-0316 or email info@heatherhayes.com today.


[1] Di Forti, Marta et al. “High-potency cannabis and the risk of psychosis.” The British journal of psychiatry : the journal of mental science vol. 195,6 (2009): 488-91. doi:10.1192/bjp.bp.109.064220

[2] “2018 NSDUH Detailed Tables | CBHSQ Data”. Samhsa.Gov, 2018, https://www.samhsa.gov/data/report/2018-nsduh-detailed-tables.

[3] CNBC, 2021, https://www.cnbc.com/2021/01/06/marijuana-united-states-law.html. Accessed 17 Mar 2021.

[4] “What Is The Scope Of Marijuana Use In The United States? | National Institute On Drug Abuse”. National Institute On Drug Abuse, 2020, https://www.drugabuse.gov/publications/research-reports/marijuana/what-scope-marijuana-use-in-united-states.

[5] : “Sex And Gender Differences In Substance Use | National Institute On Drug Abuse”. National Institute On Drug Abuse, 2021, https://www.drugabuse.gov/publications/research-reports/substance-use-in-women/sex-gender-differences-in-substance-use.

[6] Herrmann, Evan S. et al. “Sex Differences In Cannabis Withdrawal Symptoms Among Treatment-Seeking Cannabis Users.”. Experimental And Clinical Psychopharmacology, vol 23, no. 6, 2015, pp. 415-421. American Psychological Association (APA), doi:10.1037/pha0000053. Accessed 17 Mar 2021.

[7] “Monitoring The Future | National Institute On Drug Abuse”. National Institute On Drug Abuse, 2020, https://www.drugabuse.gov/drug-topics/trends-statistics/monitoring-future.

[8] “What Is Cannabis? Facts About Its Components, Effects, And Hazards”. Healthline, 2021, https://www.healthline.com/health/what-is-cannabis#Whats-the-definition-of-cannabis?.

[9] Hall, Wayne, and Louisa Degenhardt. “The Adverse Health Effects Of Chronic Cannabis Use”. Drug Testing And Analysis, vol 6, no. 1-2, 2013, pp. 39-45. Wiley, doi:10.1002/dta.1506. Accessed 17 Mar 2021.

[10] Chandra, Suman et al. “New Trends In Cannabis Potency In USA And Europe During The Last Decade (2008–2017)”. European Archives Of Psychiatry And Clinical Neuroscience, vol 269, no. 1, 2019, pp. 5-15. Springer Science And Business Media LLC, doi:10.1007/s00406-019-00983-5. Accessed 17 Mar 2021.

[11] Kuepper, R. et al. “Continued Cannabis Use And Risk Of Incidence And Persistence Of Psychotic Symptoms: 10 Year Follow-Up Cohort Study”. BMJ, vol 342, no. mar01 1, 2011, pp. d738-d738. BMJ, doi:10.1136/bmj.d738. Accessed 17 Mar 2021.

[12] Gobbi, Gabriella et al. “Association Of Cannabis Use In Adolescence And Risk Of Depression, Anxiety, And Suicidality In Young Adulthood”. JAMA Psychiatry, vol 76, no. 4, 2019, p. 426. American Medical Association (AMA), doi:10.1001/jamapsychiatry.2018.4500. Accessed 17 Mar 2021.

[13] Hall, Katelyn E. et al. “Mental Health–Related Emergency Department Visits Associated With Cannabis In Colorado”. Academic Emergency Medicine, vol 25, no. 5, 2018, pp. 526-537. Wiley, doi:10.1111/acem.13393. Accessed 17 Mar 2021.

[14] Caspi, Avshalom et al. “Moderation Of The Effect Of Adolescent-Onset Cannabis Use On Adult Psychosis By A Functional Polymorphism In The Catechol-O-Methyltransferase Gene: Longitudinal Evidence Of A Gene X Environment Interaction”. Biological Psychiatry, vol 57, no. 10, 2005, pp. 1117-1127. Elsevier BV, doi:10.1016/j.biopsych.2005.01.026. Accessed 17 Mar 2021.

[15] Schoeler, Tabea et al. “Association Between Continued Cannabis Use And Risk Of Relapse In First-Episode Psychosis”. JAMA Psychiatry, vol 73, no. 11, 2016, p. 1173. American Medical Association (AMA), doi:10.1001/jamapsychiatry.2016.2427. Accessed 17 Mar 2021.

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