Abstract Objective COMT rs4680 (Val158Met) genotype moderates the effect of cannabis on the age of onset of psychosis (AoP). We investigated the association between rs4680 and AoP, after adjusting for relevant covariates, in a Canadian Caucasian sample. Methods One hundred and sixty‐nine subjects with psychosis were recruited. AoP, defined as age of DSM‐IV diagnosis was established using the...