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Adolescent cannabis use moderates link between genetic risk for schizophrenia, brain development

Cannabis use in adolescence moderated the association between genetic risk for schizophrenia and cortical maturation among males, according to study findings in JAMA Psychiatry.

“Given the solid epidemiologic evidence supporting a link between cannabis exposure during adolescence and schizophrenia, we investigate 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, as assessed with the recently developed polygenic risk score,” Leon French, PhD, of the Rotman Research Institute in Toronto, and colleagues wrote.

Researchers analyzed cannabis use, brain imaging data and polygenic risk scores for schizophrenia of 1,577 participants, aged 12 to 21 years, from the Canadian Saguenay Youth Study, the IMAGEN Study and the Avon Longitudinal Study of Parents and Children.

Cannabis use in early adolescence was negatively associated with cortical thickness among males with a high polygenic risk score.

This association was not observed among males with low risk or females with low or high risk for schizophrenia.

Among participants in the Canadian Saguenay Youth Study, higher risk scores were associated with lower cortical thickness among males who used cannabis (P = .009).

Among participants in the IMAGEN Study, cannabis use interacted with increased risk scores in relation to a change in decreasing cortical thickness from ages 14.5 years to 18.5 years (P = .02).

Avon Longitudinal Study of Parents and Children study participants who used cannabis most frequently (ie, at least 61 occasions) had lower cortical thickness compared with those who never used cannabis (P = .02) and those with low use (ie, less than 5 occasions) (P = .004).

Overall, the study findings indicate cannabis use in early adolescence moderates the association between genetic risk for schizophrenia and cortical maturation among males. This has implications for underlying processes of cortical maturation, according to researchers.

“Several consequences of cannabis exposure were not measured in either the Pagliaccio, et al or French, et al studies, and neither included people with psychopathologies that are often comorbid and that may be consequent to cannabis use,” David Goldman, MD, of the National Institute on Alcohol Abuse and Alcoholism, wrote in an accompanying editorial. “When cannabis changes the brain, whether for good or more usually for bad, we need to learn whether the effects are pharmacologic in nature or due to shifts in socialization, study, work, exercise, or use of other psychoactive agents.” – by Amanda Oldt

Disclosure: French and Goldman report no relevant financial disclosures. Please see the full study for a list of all other authors’ relevant financial disclosures.