Offspring reported on substance use of all siblings regardless of sibling participation in the study. Sibling problem drinking was defined by offspring report that their sibling was ever an excessive drinker or that drinking ever caused problems with health, school, family, police or other problems. Sibling illicit drug use was based on offspring report that siblings ever used marijuana, cocaine, stimulants, ecstasy, opiates, hallucinogens, PCP, sedatives, solvents or inhalants, (not counting any if taken as prescribed by a doctor).
