There is a growing body of evidence that marijuana causes a number of health problems, but this study is especially sobering, as it encompassed 463,396 adolescents: Adolescents who use cannabis could face a significantly higher risk of developing serious psychiatric disorders by young adulthood, according to a large study published in JAMA Health Forum. The longitudinal study followed 463,396 adolescents ages 13 to 17 through age 26 and found that past-year cannabis use during adolescence was associated with a significantly higher risk of incident psychotic (doubled), bipolar (doubled), depressive and anxiety disorders.Good Lord. Cannabis use preceded psychiatric diagnoses by an...