Results from the biometric analyses indicate that total heritability is essentially constant across the diagnoses, and the genetic correlation between diagnoses approaches unity. Thus, the familial component of liability to alcohol problems is sufficiently captured by the new diagnosis and largely consistent with the previous criteria. However, we also found evidence of modest, but significant, diagnosis-specific genetic factors. There are significant differences in symptom endorsement rates between the diagnoses (Table 1), which results in a somewhat different profiles across the diagnoses; this could certainly correspond to a shift in relevant genetic influences. To ensure that the results were not an artifact of model structure, we reversed the order of the variables and re-ran the analysis; as expected since both variations are equivalent, the results were not qualitatively different. Hypotheses as to the nature of these diagnosis-specific genetic influences would be purely speculative based on the analyses reported here, though molecular genetic studies could be designed to address such questions.
