(Medscape and JAMA Psychiatry) June 15, 2018
Cannabis use directly increases the risk for psychosis in teens, new research shows. 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 study included 3720 adolescents from the Co-Venture cohort, which represents 76% of all grade 7 students attending 31 secondary schools in the greater Montreal area.
Cannabis use, in any given year, predicted an increase in psychosis symptoms a year later, said Conrod. This type of analysis is more reliable than biological measures, such as blood tests, said Conrod. "Biological measures aren't sensitive enough to the infrequent and low level of use that we tend to see in young adolescents," she said.
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.
In light of these results, Conrod called for increased access by high school students to evidence-based cannabis prevention programs.
The study was published online June 6 in JAMA Psychiatry.