The effects of cannabis on the male teenage brain

Tomas Paus

Tomas Paus

“Our study shows the importance of understanding environmental influences on the developing brain in early life” says Dr Tomas Paus, of the University of Toronto’s department of psychiatry. “Given the solid epidemiologic evidence supporting a link between cannabis exposure during adolescence and schizophrenia, we investigated whether the use of cannabis during early adolescence (by 16 years of age) is associated with variations in brain maturation as a function of genetic risk for schizophrenia,” said Paus. “Our findings suggest that cannabis use might interfere with the maturation of the cerebral cortex in male adolescents at high risk for schizophrenia by virtue of their polygenic risk score. Their brains showed lower cortical thickness compared with low-risk male participants and low-or-high risk female participants who used the drug.”

The study analysed data from a total of 1,577 participants (aged 12 – 21 years, 57% male / 43% female), that included information on cannabis use, brain imaging results, and polygenic risk score for schizophrenia. The data came from the Saguenay Youth Study in Quebec, the Avon Longitudinal Study of parents and Children in the U.K., and the IMAGEN Study in the U.K., Germany, France and Ireland.

Read the full press release on the University of Toronto news site:

How cannabis use affects brains of male teenagers with high genetic risk for schizophrenia

Original research article:

French L, Gray C, Leonard G, et al. Early Cannabis Use, Polygenic Risk Score for Schizophrenia and Brain Maturation in Adolescence. JAMA Psychiatry. Published online August 26, 2015. doi:10.1001/jamapsychiatry.2015.1131.