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Does Marijuana Use Cause Psychosis?

Dr. Malik Burnett and Amanda Reiman, PhD MSW

Dear Doctors,

I have heard that cannabis use can cause certain people to develop mental disorders like psychosis especially if started at an early age, is this true?

Concerned Mother

Dear Concerned,

Thanks for your question, it is one which people have posted a number of times to this blog. The topic of mental illness, much like cannabis, has a certain stigma in everyday society. Many people who have mental health issues are afraid to discuss them publically, and the amount of resources dedicated to mental health research and support are woefully inadequate at both the state and federal level. Clearly there is a lot of work which needs to be done in this space.

In regards to your question on cannabis use and the development of mental health problems, the best analogy for where the science is on this issue, is the chicken and egg question. Research in this area shows a correlation between cannabis use and psychosis. This means that the two situations are related, but it does not mean that one situation causes the other. We know that people who have symptoms of psychosis are more likely to use marijuana, but we don’t know which comes first, marijuana use or psychotic symptoms.

What exactly are psychotic symptoms? Psychosis, quite simply, describes the condition of the mind that has lost contact with reality. The symptoms of psychosis can be divided into two categories: positive symptoms and negative symptoms. Positive symptoms, are those which reflect an increase in brain activity and include: delusions, hallucinations, paranoia, disorganized thinking, and disorganized speech.  On the other hand, negative symptoms, are those which reflect a decrease in brain activity and include: lack of motivation, decrease ability to create or receive new ideas, decreased talking, difficulty expressing emotion, and difficulty concentrating.

It is also important to note that the mental disorder of psychosis is extremely rare, with about 3 in every 100 people experiencing a psychotic episode in their lifetime. The onset of psychosis, or similar disease processes like schizophrenia, usually begin in an individual’s late teens to early twenties. This generally also happens to be around the same time when individuals have their first exposure to cannabis. The fact that these two time periods overlap makes it difficult to know if the psychosis is induced by marijuana.

There are several theories that attempt to explain the relationship between cannabis use and mental illness. They are effectively summarized on the award winning Cannabis and Psychosis: Exploring the Link website. Links and a brief synopsis are provided below:

  • The vulnerability theory: stating that cannabis use leads to the development of psychosis in people who have a family history of psychotic episodes.
  • The contributing cause theory:  stating that cannabis use is one of many factors which leads to the development of psychosis.
  • The self-medication theory: stating that individuals who have psychotic experiences, use cannabis to self-medicate in advance of being formally diagnosed with a psychotic disorder

Overall, the body of scientific literature has not been able to provide a definitive answer as to whether cannabis use causes psychosis. Compelling arguments and data have been provided to suggest that those with a predisposition for mental illness can exacerbate those symptoms by using cannabis, however some fundamental questions remain. Namely, if there is a direct link between cannabis use and psychosis, it should follow that the number of diagnoses of psychosis should rise with the increasing prevalence of cannabis use in society. This phenomenon has not been established.

Moreover, from a public policy standpoint, regulations on marijuana should include education about the possible risks for young people and those with mental health issues. As cannabis policy reform continues to take shape globally, it is clear that issues such as these should be taken into consideration.

The Doctors

Dr. Malik Burnett is a former surgeon and physician advocate. He also served as executive director of a medical marijuana nonprofit organization. Amanda Reiman, PhD, holds a doctorate in Social Welfare and teaches classes on drug policy at the University of California-Berkeley.

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