Participants were 72 adolescents ranging in age from 16 through 19 years. Thirty-six adolescents were heavy marijuana and alcohol (MJ+ALC) users, and 36 were demographically similar controls with very limited substance use histories (see Table 1). Adolescents were recruited from San Diego area schools from 2005 to 2007. Inclusionary criteria required participants and their parents or legal guardians to provide consent and comprehensive medical history. Adolescents and their parents were screened with separate, private interviews to ascertain eligibility. Exclusionary criteria for both users and controls were: DSM-IV Axis I disorder; nicotine dependence (e.g., Fagerstrom Test for Nicotine Dependence (FTND; (Heatherton, Kozlowski, Frecker, & Fagerstrom, 1991) score ≥ 3), use of psychoactive medications; chronic medical illness, history of neurological disorder, head trauma with loss of consciousness >2 minutes, learning disability or mental retardation, complicated/premature birth (<33 weeks gestation); evidence of maternal drinking (>7 drinks in a week or >4 drinks in a day) or illicit drug use during pregnancy; parental history of bipolar I or psychotic disorder; left handedness; non-fluency in English; MRI contraindications; and clinically abnormal brain anatomy. Having surpassed
