COGA Alcohol Dependence Recruitment and Assessment Protocol

Initial ascertainment of alcohol-dependent probands (designated Stage I) was performed by screening consecutive admissions at treatment facilities. Probands were assessed with the Semi-Structured Assessment for the Genetics of Alcoholism (SSAGA), a comprehensive diagnostic instrument developed for this study and now widely used [18 (link),19 (link)]. Extensive histories of substance use and abuse were gathered along with diagnostic information for multiple Axis I disorders and antisocial personality disorder. To be recruited into the COGA study, probands had to meet both the diagnostic criteria for alcohol dependence (by DSM-III-R criteria [20 ] and the criteria for definite alcoholism specified by Feighner et al. [21 (link)]); thus, the COGA sample is representative of a severely alcohol-dependent population. All first degree relatives of the probands were invited to participate. Children and adolescents in the families were assessed with complementary age-appropriate instruments (C-SSAGA, child and adolescent versions). A set of control families was ascertained to provide normative measures; they were not screened to eliminate those with psychiatric disorders, and are similar to a general population sample. Written informed consent was obtained from all subjects, and the Institutional Review Boards (IRB) of each collaborative site approved all procedures. A more complete description of the recruitment procedures can be found in Begleiter et al. [1 (link),22 ]. Over 13,000 individuals have been interviewed to date.
A subset of COGA families with at least three alcohol-dependent first degree relatives (designated Stage II) was identified as suitable for a genetic linkage study [1 (link)]. These families were extended by diagnostic assessment of more distant relatives in branches reached through an affected member. The Stage II families participated in a more comprehensive multi-domain assessment with an electrophysiologic evaluation of event-related potentials (ERP), event-related oscillations (EROs) and resting electroencephalogram (EEG), endophenotypes associated with alcohol dependence [23 (link),24 ] that are more proximal to genes and may provide measures of the liability underlying a predisposition to alcohol dependence and related disorders.