A total of 716 EAs were recruited at either the University of Connecticut Health Center or the VA Connecticut Healthcare System-West Haven campus. Among them, 136 were affected with comorbid AD and DD (“AD+DD”), 166 were affected with AD and no comorbid drug dependence (“AD-only”) and 414 were healthy controls. Details of sex and age distributions are shown in Table 1. Each affected subgroup was examined separately in relation to the 414 control subjects for association analyses. AD+DD subjects met lifetime DSM-III-R [APA, 1987] or DSM-IV [APA, 1994] diagnostic criteria for AD and also met diagnostic criteria for cocaine dependence (CD) and/or opioid dependence (OD) (see Table 1). Healthy controls, recruited by advertisement from the general population, were screened to exclude subjects with AD, DD, major Axis I psychiatric disorders such as mood disorders, major anxiety disorders, and psychotic disorders (i.e., schizophrenia or schizophrenia-like disorders). The Structured Clinical Interview for DSM-III-R (SCID-III-R) or DSM-IV (SCID-IV), the Computerized Diagnostic Interview Schedule for DSM-III-R (C-DIS-R), the Schedule for Affective Disorders and Schizophrenia (SADS), or an unstructured interview were used for screening. Many of the subjects were not characterized with respect to ND, so this diagnosis could not be considered.
