The twin studies we identified from the literature search, including information about the cohort, sample sizes, measure used, and A, C, and E estimates, are presented in Table 1 (cannabis use initiation) and Table 2 (problematic cannabis use). The studies selected for the meta-analysis are shown in bold. One cohort (US, Vietnam Era Twin Registry [VETR]) only used male participants, so we could not include this cohort into our meta-analyses for females.
