Participants were excluded from the current analyses if they lacked good-quality structural MRI data available (N=17), were missing relevant interview/questionnaire data (N=10), or screened positive for tetrahydrocannabinol on a urine screen but reported not using cannabis within the last 12 months (N=16). This resulted in a final sample size of 483 individuals (262 ever using cannabis). In analyses involving sibling pairs (eMethods S1), 36 individuals who did not have a full sibling or twin in the present data release were excluded. As sex is significantly related to both cannabis use and brain volumes, the inclusion of discordant opposite-sex non-twin sibling pairs (all twin pairs were same-sex), can result in statistical confounds. Therefore, we excluded 145 opposite-sex pairs, resulting in 241 sibling pairs (50 MZ, 45 DZ, and 146 non-twin siblings [mean sibling age difference=3.69 years]), including 89 same-sex pairs discordant for cannabis exposure, 81 concordant for cannabis exposure, and 71 concordantly unexposed pairs (eTable 1).
