Comparison of alcoholism subtypes as moderators of the response to sertraline treatment.
BACKGROUND
A variety of typologies have been used to categorize alcoholism's diverse manifestations. Although the most widely studied typologies are dichotomous ones based on genetic epidemiologic findings or using cluster analytic methods, recent efforts have utilized a single item or the onset of a diagnosis of alcohol dependence to subtype individuals based on the age of alcoholism onset. We compared 3 different methods to subtype alcoholics.


METHODS
This secondary analysis used data from 134 alcohol-dependent participants in a placebo-controlled trial of sertraline (Kranzler et al., 2011). We compared cluster analysis to distinguish 2 risk/severity subtypes (Babor et al., 1992) with 2 age-of-onset subtypes (i.e., based on the age of onset of problem drinking or the age at which alcohol dependence criteria were first met).


RESULTS
Each method yielded subgroups that differed significantly from one another on demographic and clinical measures. Although concordance was high between the 2 age-of-onset methods, it was poor between the age-of-onset methods and the cluster analysis-derived approach. All 3 subtyping approaches significantly moderated the effects of sertraline or placebo, but only in the L'L' genotype group, as originally reported (Kranzler et al., 2011). In all cases, sertraline treatment was superior to placebo in later-onset individuals and inferior to placebo in the earlier-onset groups.


CONCLUSIONS
Because age-of-onset subtypes can be defined retrospectively on an individual basis, they may be more clinically useful than cluster-derived subtypes, which require group data. Because the 2 age-of-onset measures we examined appear to have comparable validity, a single item is easier to use as a measure of the age of onset of problem drinking.