556 participants. The phenotypic data obtained from subjects who reported at more than one time point were checked for consistency, and unreliable measures were discarded. Due to inconsistencies, 284 self-reported measures were dropped. Next, the measurements were collapsed into a dichotomous phenotype (i.e., ever/never used cannabis). Furthermore, we included in the analysis only family members for whom both phenotypes and genotypes were available, i.e., N = 6744 participants. Of these, 5387 individuals reported never to have used cannabis, whereas the remaining 1357 individuals had initiated cannabis use. The age at the time of the last survey ranged from 10.5 to 94 years (mean age = 39.09, SD = 17.45). The participants were clustered within 3479 families varying in size from 1 to 9 family members (i.e., parents, siblings, spouses). More than half of the sample (60.9 %) consisted of females.
