R e su lt s : The methamphetamine cohort had a significantly higher risk of schizophrenia than the appendicitis group (hazard ratio=9.37) and the cocaine, opioid,and alcohol groups (hazard ratios ranging from 1.46 to 2.81), but not significantly different from that of the cannabis group.The risk of schizophrenia was higher in all drug cohorts than in the appendicitis group.