The main analyses controlled for demographic factors of sex (female>male), ethnicity (White>not; African-American>not), age, zygosity (MZ>not; DZ>not), total household income (eMethods S3), and age-adjusted picture vocabulary scores as a proxy for crystallized intelligence20 (eMethods S4) – henceforth, these are referred to as primary covariates. Follow-up regression analyses controlled for a variety of other potential confounds, including personality, impulsivity, other substance use, and comorbid psychopathology (eTable 10). See eMethods S5 for rationale and assessment details.
