A Dutch study has found that marijuana use before age 17 was associated with a 50-percent increase in the risk of later suffering an episode of depression, although researchers said that the association weakened when a history of conduct disorders was figured in, Reuters reported July 6.

Researchers said the findings don’t prove that youthful marijuana use leads to depression, or vice-versa. However, study author Ron de Graff of the Netherlands Institute of Mental Health and Addiction said it is possible that drug use could affect the still-developing adolescent brain. “Early cannabis use may have important consequences for later mental health,” he said. “We know now — also from other studies — that cannabis use is not without negative consequences.”

The study was published in the American Journal of Epidemiology.