Paying the Piper: Marijuana Now, Psychosis Later

Charles P. Vega, MD


July 13, 2018

Hello. I'm Dr Charles Vega, and I am a clinical professor of family medicine at the University of California at Irvine. Welcome to Medscape Morning Report, our 1-minute news story for primary care.

A recent prospective study involving almost 4000 adolescents and using a novel multilevel approach that examined within-person differences found a strong correlation between cannabis and psychosis.

From 13 to 16 years of age, participants completed an annual online survey to self-report symptoms and frequency of cannabis use. The study revealed statistically significant positive associations, at every time point, from use to psychosis symptoms reported up to a year later.

Cannabis use, in any given year, predicted an increase in psychosis symptoms a year later. And the effect was observed for the entire cohort, meaning that all young users faced this psychosis risk, not just those with a family history or a biological factor that increased their susceptibility to the effects of cannabis. The researchers contend that this analysis is more robust than previous research in that it assessed users at multiple time points and looked at within-person change.

Given the widespread move towards legalization, there is a need to understand whether use has a causal role in development of psychiatric illness. This study begins to provide an answer.


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