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]. 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 [23,24] that are more proximal to genes and may provide measures of the liability underlying a predisposition to alcohol dependence and related disorders.
