Analyses of the COGA data set in one ethnic group with examinations of alternative definitions of alcoholism.

We used GENEHUNTER and GENEHUNTER-PLUS to search for linkage with the markers in the Collaborative Study on the Genetics of Alcoholism (COGA) data set in a single ethnic group. Analyses of a complex disorder such as alcoholism depend on the definition of affection status. The COGA study provides two definitions of alcoholism (variables ALDX1 and ALDX2). To identify more severely affected alcoholics that might be more homogeneous genetically, we developed two other ways of characterizing subjects as alcohol dependent: (1) by combining the symptom variable values equally into a 24-point scale and (2) by weighting optimally the symptoms and other descriptive variables into a single score using logistic regression. We applied these definitions within a single ethnic group to map alcoholism-related loci. We found two regions on chromosome 1 that have adjacent markers significant at p-values < or = 0.05. ALDX1 provided the highest Z-scores compared to the alternatives.