To investigate potential explanations for the limited overlap in linkage findings when the temporal clustering of symptoms was and was not required for the alcohol dependence diagnosis, we conducted a post hoc analysis comparing the average age-of-onset of those symptoms associated with linkage peaks for the alcohol dependence diagnosis when the temporal clustering of symptoms was and was not required. Regions that showed linkage to both phenotypes (i.e., chromosome 1 at 12 cM and chromosome 8 at 163 cM) were attributed to the phenotype that showed the higher LOD score. A nonparametric, rank-order Mann-Whitney U test suggested that symptoms linked to peaks for the alcohol diagnosis when the temporal clustering of symptoms was required showed a later age-of-onset than symptoms linked to peaks when the temporal clustering of symptoms was not required (U = 48.50, p = .038).
