Cases met criteria for DSM-IV cannabis dependence(30), which included withdrawal (i.e., 3 or more of 7 criteria) in COGA and SAGE but not in CATS or OZALC+. Controls did not meet criteria for cannabis dependence but reported a lifetime history of ever having used cannabis, even once. Follow-up analyses of top loci examined whether excluding those with DSM-IV cannabis abuse or 1–2 dependence criteria modified the results. A natural log-transformed (to account for skewed data) count of DSM-IV dependence criteria (0–6, excluding withdrawal; adding “1” for 0 values) was also analyzed (n=8,050). Finally, the effect of comorbid DSM-IV alcohol, nicotine and opioid dependence was investigated by examining their association with top loci in post hoc analyses.
