Evidence is mounting that regular marijuana use increases the chance that a teenager will develop psychosis, schizophrenia or a pattern of unusual thoughts or perceptions, earlier than they might have had they not used cannabis. Heavy marijuana use between the ages of 15 and 17, a critical period for brain development, could result in the onset of psychosis in those prone to the disorder, new research suggests (1).
“With several states easing marijuana laws or even legalizing the drug altogether, both adolescents and parents might pay heed to this warning about the potential for the earlier onset of psychotic illness in regular marijuana users,” says Dr. Stephen Brockway, The Meadows Psychiatrist.
It’s important to keep in mind that this research does not mean marijuana can cause psychosis. It only shows a relation between smoking pot and developing psychosis or schizophrenia earlier than one otherwise might have. Data from the Allied Cohort on the Early course of Schizophrenia (ACES) II project, a secondary analysis of ACES, showed those who regularly smoked marijuana (at least more than twice a week) aged 15-17 years experienced first episode psychosis an average of almost 4 years earlier than their counterparts with first episode psychosis who did not use cannabis (1).
Predictors that cannot be modified regarding the age of onset for development of psychosis are male sex and family history of psychosis. Young adults with a parent or sibling affected by psychosis have a roughly one in 10 chance of developing the condition, whether or not they smoke marijuana (2).
The study included 247 hospitalized patients who had experienced first episode psychosis. Most study participants were single, male and African American. Nearly half of the patients had not graduated from high school, and almost 60% had been incarcerated. It was discovered that the average age of prodromal symptoms was 19 years, age at onset of psychotic symptoms was 21 and age of hospitalization was 23 (1).
Researchers asked the patients’ detailed questions about their individual marijuana use and just fewer than 80% reported having used the drug. The average age of psychosis onset was 21 years in those who used cannabis between the ages of 15 and 17, compared to those with no cannabis use during that time period, which were roughly 23 to 24 years of age. The amount of marijuana smoked was also a predictor of age of onset for those under 18 years old.
Teen use of marijuana may be particularly harmful because the teenage brain is still a work in progress. Areas of the brain responsible for judgment and problem solving are still making connections with the emotional centers of the brain. It is possible that smoking marijuana could derail the natural process of brain growth, which in turn could increase a young person’s vulnerability to psychotic thinking.
Delay in psychosis onset is important because it improves outcomes in the severity of symptoms and disability level. The later in life psychosis symptoms arise, the more one has been able to accomplish, such as graduate from high school. This in and of itself is associated with better physical health, better mental health and better social outcomes over the course of a life span (1). Despite the growing evidence of the relationship between marijuana and psychosis, further research is needed to determine causality.
Many doctors explain how the link between marijuana and psychotic disorders is important to be aware of for patients with a family history of schizophrenia or other psychotic disorders, but there is no evidence in regards to marijuana being a cause for these disorders. It is most plausible to conclude that cannabis use precipitates schizophrenia or other psychotic disorders in individuals who are already vulnerable because of family history (3).