Cannabis use was operationalized as a 6-level categorical variable reflecting number of times used over the lifetime, with the lowest level being all non-users and the remaining levels representing 20% intervals (quintiles) for frequency of use. Given that males had higher rates of initiation (68.8% of males vs. 53.2% of females reported ever use) and reported heavier use, quintiles were calculated separately by sex. As in the case of alcohol consumption, the cannabis use variable is therefore an indicator of heaviness of use relative to same-sex peers. Frequency of use is reported by sex in Table 1.
