Development and construct validity of the composite measures for the phenotypes used in this study have been described extensively in a development report (Hicks et al., 2011). Phenotype values are factor scores computed from hierarchical factor analysis of items measuring substance use and behavioral disinhibition. Nicotine Use/Dependence (NIC) included lifetime symptoms of DSM-III-R nicotine dependence, as well as frequency and quantity of nicotine use during the period of an individual’s heaviest use. Alcohol Consumption (CON) included number of lifetime intoxications, maximum number of drinks consumed in a 24-hour period, and frequency of alcohol use during the period of heaviest use. Alcohol Abuse/Dependence (DEP) included the symptoms from several diagnostic systems including DSM-III-R, DSM-III, Research Diagnostic Criteria, and Feighner Criteria that assess pathological use of alcohol organized around the content domains of physiological tolerance and withdrawal, social and occupational problems due to drinking, and compulsive drinking (e.g., little time for anything but drinking). Drug Use (DRG) included the number of lifetime marijuana uses, a count of the number of classes of illicit drugs a person had ever tried (e.g., stimulants, hallucinogens,
