Cannabis use directly increases the risk for psychosis in teens, new research suggests.
A large prospective study of teens shows that "in adolescents, cannabis use is harmful" with respect to psychosis risk, study author Patricia J. Conrod, PhD, professor of psychiatry, University of Montreal, Canada, told Medscape Medical News.
The effect was observed for the entire cohort. This finding, said Conrod, means that all young cannabis users face psychosis risk, not just those with a family history of schizophrenia or a biological factor that increases their susceptibility to the effects of cannabis.
"The whole population is prone to have this risk," she said.
The study was published online June 6 in JAMA Psychiatry.
Rigorous Causality Test
Increasingly, jurisdictions across North America are moving toward cannabis legalization. In Canada, a marijuana law is set to be implemented later this year.
With such changes, there's a need to understand whether cannabis use has a causal role in the development of psychiatric diseases, such as psychosis.
To date, the evidence with respect to causality has been limited, as studies typically assess psychosis symptoms at only a single follow-up and rely on analytic models that might confound intraindividual processes with initial between-person differences.
Determining causality is especially important during adolescence, a period when both psychosis and cannabis use typically start.
