Evidence of linkage in subtypes of alcoholism

We believed that subtyping alcoholism might be an efficient strategy for mapping susceptibility genes. Cluster analysis is one of the possible statistical techniques for such a purpose. We required that, ideally, the variables to be used in cluster analysis should be: 1) related to alcoholism, 2) related to the severity of alcoholism, and 3) familial, i.e., correlated within families. Only three variables met all three conditions. Those included age of onset of ALDX1, smoking, and TPQ-HA. A global score of symptoms of alcoholism was systematically introduced as one of the variables composing a subset for cluster analysis, although this score did not show any familial aggregation. Our strategy led to a strong evidence of linkage at D15S230 in only 20 families whose members are mainly characterized by heavy smoking.