Home » Blog » Breaking the Camel’s Back: Understanding the Relationship Between THC and Psychosis

Breaking the Camel’s Back: Understanding the Relationship Between THC and Psychosis

Nov 2, 2020

Dr. John Dyben, DHSc, MCAP, CMHP – Chief Clinical Officer

The cannabis plant has myriad chemical compounds (literally hundreds), and various cannabis strains tend to have these compounds in different amounts.  Perhaps the most well-known chemical in cannabis is Δ-9-tetrahydrocannabinol, most commonly referred to as THC.  This is the primary psychogenic compound that causes the effect of “getting high.”

For many years now, scientists have been studying a link between THC and psychosis.

Numerous studies have found that high-frequency THC use is associated with a greater risk of psychosis.  In healthy adults without a history of mental health conditions, high dose THC can cause symptoms that mimic psychosis similar to those with schizophrenia.  These symptoms can last while the person is under the influence, to as long as a month after. For many, frequent and high dose THC use has been implicated in contributing to psychotic episodes that led to lasting and persistent psychosis and even schizophrenia.

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For those who do develop schizophrenia or some other form of persistent psychosis, continuing to use THC contributes to worsening overall mental health.

Prevailing wisdom, for now, is that those who develop persistent psychosis most likely had other factors that predisposed them.  For some, THC may have been “the straw that broke the camel’s back” and pushed someone over the edge into a psychotic disorder.

Today, healthcare practitioners report encountering patients suffering from psychosis that they suspect is drug-induced or exacerbated. They will say, “…but the only thing this patient used was marijuana.” The sentiment being that cannabis has long been thought of as mostly benign and should not have such a significant negative role in people’s mental health. Unfortunately, this is not the case, especially today.

Research that correlates THC to psychosis also indicates that the link is associated with high doses of the drug. In fact, the most dangerous combination is someone who starts using at a young age, uses often, and uses in high doses.

Until the late 1970s or early 1980s, THC levels that most cannabis people could obtain was about 2% or less.  Today, THC concentration across the gamut of products can run higher than 90%.  Like alcohol, a given amount of the substance may have a greater impact than the same amount of another substance. So, 4 ounces of beer would impact a person differently than four ounces of wine, which would be different from four ounces of liquor. Though the size of the pour is the same, the concertation of the drug is different.

Today, cannabis users are putting vastly greater THC quantities into their system, and these wildly higher doses are leading to increased problems.  In turn, when the family doctor says, “My patient wasn’t doing ‘hard’ drugs. He was just smoking pot.”, she is likely thinking about a low THC concentration cannabis that she has referenced in her mind rather than the extremely high levels of a potent psychoactive drug that we have today.

But what about the medicinal effects of THC?

There is much talk about cannabis as a medicine, especially in today’s world of mass-information (and more often mass-disinformation) available through the internet. Often, it is based on speculation and hearsay, as opposed to science and research.

So here are a few essential facts based on what we know from research up to this point:

  • The research on the efficacy of cannabis for improving health conditions has yet to find strong evidence for treating most conditions.
  • The strongest evidence that cannabis has a helpful impact on medical symptoms as much or more than what other, safer, interventions can accomplish is found in studies related to symptoms of spasticity, ticks, and seizures. Research also indicates reports of sleep improvement in patients being treated with cannabis but the mechanism for this improvement is unknown.
  • There is no research whatsoever that indicates any health benefit from cannabis with higher THC concentration levels.

THC is only one of the chemicals in cannabis that has been studied for medicinal value. Another important chemical, Cannabidiol (CBD), has been the subject of much attention in this area. CBD does not have the same psychoactive properties as THC. Though CBD’s safety and efficacy are not fully understood, the prevailing thought based on current research is that CBD may be more important than THC to improve medical conditions and has less risk. Additionally, evidence suggests that CBD may be protective against some of the risks associated with THC.  Again and importantly, the research on CBD is very preliminary and not at all comprehensive.

Given the risks of psychosis associated with THC, any medicinal use should be considered only when there is no better alternative, and under the direct care and monitoring of medical professionals.

This is particularly true for those who are young and/or have increased risk for addiction, psychosis, or other mental health condition.  The brain seems to be most susceptible to THC’s harmful effects during the years that it is in its primary development. This development begins in utero and continues well into the mid-20s.

During these years, THC use, particularly frequent and high-dose, is playing Russian Roulette with the brain. Unlike the old image of “reefer madness,” implying one puff on a joint would drive anyone to wild and violent behavior, we know that several factors contribute to how a person’s brain will respond. Age, genetic predisposition, medical and psychological history, current physical, and mental health are just a few. Some may be known factors, while other people may be completely unaware of it.

What we do know is that around 9% of all people who try THC will become addicted. That increases to about 17% when a person’s first use is in their teen years.

Once a person is addicted, they will continue to use despite the negative consequence, even the consequences of psychosis. Thus, the best recommendation is to avoid TCH altogether during the years that the brain is developing. After that time, anyone considering using cannabis in any form should consider all risks carefully and make decisions based on the best available science rather than a rumor, misinformation, and outdated or disproven ideas.

Your brain is worth it, and it’s the only one you get!


Cash, M. C., Cunnane, K., Fan, C., & Romero-Sandoval, E. A. (2020). Mapping cannabis potency in medical and recreational programs in the United States. PloS one, 15(3), e0230167.

Colizzi, M., Ruggeri, M., & Bhattacharyya, S. (2020). Unraveling the intoxicating and therapeutic effects of cannabis ingredients on psychosis and cognition. Frontiers in Psychology, 11.

DSouza, D. C., Radhakrishnan, R., Sherif, M., Cortes-Briones, J., Cahill, J., Gupta, S., … & Ranganathan, M. (2016). Cannabinoids and psychosis. Current pharmaceutical design, 22(42), 6380-6391.

Gage, S. H. (2019). Cannabis and psychosis: triangulating the evidence. The Lancet Psychiatry, 6(5), 364-365.

Hahn, B. (2018). The potential of cannabidiol treatment for cannabis users with recent-onset psychosis. Schizophrenia Bulletin, 44(1), 46-53.

National Institutes of Health (November 2019). Cannabis (Marijuana) and Cannabinoids: What You Need To Know.

Sideli, L., Quigley, H., La Cascia, C., & Murray, R. M. (2020). Cannabis use and the risk for psychosis and affective disorders. Journal of dual diagnosis, 16(1), 22-42.

Stuyt, E. (2018). The problem with the current high potency THC marijuana from the perspective of an addiction psychiatrist. Missouri medicine, 115(6), 482.


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