Multiple epidemiological and genetically informed studies have documented the importance of age at onset of alcohol dependence (AO-AD) as a key feature of sub-types of alcoholism that vary in etiology and severity.1, 2, 3, 4, 5, 6 For instance, Cloninger et al.3 identified Type I and II alcoholics who were distinguished by, among other features, age at onset of alcohol problems. Similarly, Babor et al.2 defined Type A and B alcoholics—the latter were distinguished by early onset of alcohol problems. Across these typologies, early-onset problematic use was consistently associated with a more severe form of the disorder, which was often accompanied by polysubstance use and other psychiatric comorbidity, particularly externalizing disorders.
