Familial rates of affective and substance use disorders in patients with first-episode mania

Background: One explanation for the high co-occurrence between bipolar and substance use disorders is that substance abuse may precipitate affective s ymptoms in patients who otherwise may have not had the genetic risk for dev eloping an affective illness. Previous studies comparing familial rates of affective illness between bipolar patients with and without alcohol use hav e provided conflicting results. We hypothesized that patients with bipolar disorder and antecedent alcohol abuse would have lower familial rates of af fective illness than bipolar patients without antecedent alcohol abuse. Met hods: Family history data were obtained on 275 first-degree relatives of 51 patients hospitalized for a first manic episode using the Family History R esearch Diagnostic Criteria. Results: Patients with bipolar disorder and an tecedent alcohol abuse had lower familial rates of affective illness than p atients with bipolar disorder without antecedent alcohol abuse (two-tailed Fisher's exact, P = 0.003). There was no statistically significant differen ce in the familial rates of affective illness between bipolar patients with and without antecedent drug abuse (other than alcohol). Patients with bipo lar disorder and antecedent alcohol abuse had a significantly older age of onset of affective illness (27.6 years) than patients with bipolar disorder without antecedent alcohol abuse (20.6 years, z = 3.3, df = 1, P = 0.0009) . There was no statistical difference in age of onset of affective illness between the patients with antecedent drug abuse and the patients without an tecedent drug abuse. Limitations: Future studies with a larger number of bi polar patients, direct structured interviews of family members and better d ifferentiation between substance abuse and dependence syndromes are needed to extend and replicate this pilot study. Conclusions: Our study suggests t hat there may be a subset of bipolar patients who have antecedent alcohol a buse and a subset who develop alcohol abuse after the onset of bipolar diso rder. We further speculate that alcohol abuse may precipitate mania in some patients with bipolar disorder. (C) 1999 Elsevier Science BN. All rights r eserved.