Cannabis dependence symptoms were queried in all individuals who reported having used cannabis on at least a monthly basis (and a total of 11 or more times over the lifetime) and coded 0 for those who had used cannabis but did not meet this minimum frequency. Drug dependence was not the primary focus of the interview, so to reduce respondent burden, an abbreviated cannabis dependence assessment based on the following four criteria was conducted: 1) using more frequently or over a longer period of time than intended, 2) needing larger amounts to achieve the same effect (tolerance), 3) continued use despite cannabis-induced emotional problems, and 4) recurrent desire to cut down on use. (Analyses examining these modified criteria against full DSM-IV diagnostic criteria have yielded sensitivity and specificity estimates of 96.7% and 94.6%, respectively [Lynskey et al., 2002]).
