A continuous measure of age at onset of cannabis use was associated with rVUS, regardless of covariate adjustment (OR=0.58, 95% CI 0.49-0.68; i.e. lower age associated with higher rVUS; Table S2). When twin pairs with differing ages at first use were considered, rVUS was more commonly reported in the twin reporting the earlier age at first use (Table S3 for details). Other dichotomous definitions of adolescent cannabis use (e.g. <16 years, <18 years) showed similar results; however, the significance of the point estimate relied heavily on the discordant pair sample size (Table S4).
