Two sets of linkage analyses were performed using two different phenotypes: the phenotype of alcoholism defined by each of the two criteria: DSM-IIIR and DSM-IV. These were coded as dichotomous variables, and denoted respectively as Alc1 and Alc2. The following covariates were used in all linkage analyses: dichotomous indicator of habitual smoking; dichotomous indicator of whether an individual was Black (derived from ethnicity); dichotomous indicator of whether an individual was White (derived from ethnicity); age at interview; square of age at interview; cube of age at interview. The results of the initial linkage analyses are shown in Figure 1. The differences in linkage signal when using the two different definitions of alcoholism (Alc1 for DSM-III-R, Alc2 for DSM-IV) are seen throughout the genome.
