Marijuana and Risk of Psychosis in Adolescents

Law makers in New Jersey are preparing to pass laws that will legalize the use of recreational marijuana, making it the 10th state in the US to do so.


Because federal law still prohibits marijuana use, there has been relatively little research conducted on its use and effects compared to other substances, yet we see this trend reversing as more states take steps towards legalization.

Of particular interest to parents and adolescent healthcare providers such as myself, is safety of cannabis in young people, whose brains are still developing.

While for some people medical or recreational marijuana is very helpful, for others it may pose some risks. The group that may be most vulnerable to negative effects are adolescents with predisposition to psychosis.

A number of older studies pointed out the risk of psychosis in adolescents using cannabis and, new large research study also suggests that teens who use marijuana may have greater odds of experiencing psychotic episodes.

:: Related article: Cannabis and Mental Health ::

A longitudinal study published in JAMA Psychiatry in March 2018 found that young people who use cannabis regularly were more than twice as likely to experience psychosis including hallucinations or delusions. The study followed more than 5300 British teens age 14 to 19 who reported both consistent cigarette smoking and the use of marijuana. Knowing that many people commonly engage in both, the idea was to isolate and separate the health effects of each substance.


Results revealed that among participants who started using cannabis in their early teens, there was a 4% increase in their risk of having a psychotic episode by age 18. Perhaps even more alarming was the discovery that young people who started using cannabis later in their teenage years had nearly 12% greater odds of having a psychotic experience by age 18. Even when potentially confounding factors like alcohol use, social status, and family mental health history were accounted for, the connection between cannabis and psychosis remained present.

Researchers also noted that while cannabis use was significantly associated with increased risk for psychotic experiences, cigarette smoking was not. There was also little evidence that psychotic experiences in childhood led to later cannabis use.

Researchers did note that one potential contributing factor to the results could be a predisposition to mental health challenges. Individuals who affected by a condition known as "attenuated psychotic syndrome," are at a higher risk for eventual development of a full-blown psychotic illness. Symptoms of attenuated psychotic syndrome include visual illusions or magical thinking that do not quite reach the level of delusions. People in this category are at higher risk of cannabis triggering a psychotic disorder.

On the whole, the current body of scientific evidence still leaves many questions unanswered. One is about the safety and efficacy of medical marijuana. While medical marijuana may have a number of benefits (and there is currently active research to clarify which strains and components of cannabis may be safest and most beneficial for a variety of medical and mental health conditions), research does suggest we use caution when it comes to prescribing it for teens who are already at risk for psychosis. While the overall rate of psychosis and schizophrenia is low in the population, findings suggest a need to protect individuals who, as a result of cannabis use, do show early signs of psychosis, prodromal schizophrenia (the first stage of the disease before active schizophrenia sets in), or bipolar disorder.


The fact is that cannabis is one of the most widely used illicit substances in the United States, and while popular culture tends to have a benign view of its effects, research has revealed that there may be correlation between its consumption and certain psychiatric disorders especially in adolescents. With the increasing trend toward nationwide legalization, the best option for each individual is an honest assessment of its potential risks versus benefits and lots of research on the effects of different strains and on safe and responsible dosing.

Dr. Lewis is a medical marijuana prescriber in New York State and helps individuals assess their personal risk for marijuana use, and to develop best practices that minimize risk when using cannabis. New York State allows medical marijuana prescribing for patients with PTSD and Chronic Pain diagnoses, in addition to a number of medical condition diagnoses.