Clinical features related to age at onset in bipolar disorder

Background: Early age at illness onset has been associated with poor functional and syndromal outcome in bipolar disorder, although debate remains about the likely robustness of this variable, especially while controlling for other illness parameters. Method: Fifty-six consecutive bipolar outpatients underwent semistructured interviews to assess psychopathology and outcome. We hypothesized that early age at onset would be linked with more prevalent rapid cycling, psychosis, comorbid substance abuse, and suicide attempts. Results: Illness onset before age 19 arose in 46% of subjects. Separate logistic regression analyses revealed that onset before age 19 was associated with developing comorbid substance abuse/dependence (OR=7.714, 95% CI=1.863-31.944, Wald χ ²=7.949, df=1, P=0.005), as well as the eventual development of rapid cycling (OR=6.000, 95% CI=1.250-25.893, Wald χ ²=5.348, df=1, P=0.021). No significant or near-significant associations were observed between age at onset and lifetime suicide attempts or lifetime psychosis. After an initial manic or mixed episode, delaying the introduction of antidepressants tended to be protective against the eventual development of rapid cycling (OR=0.927, 95% CI=0.856-1.004, Wald χ ²=3.440, df=1, P=0.064). Limitations: The sample size may have been too small to detect group differences of small magnitude. The use of retrospective life chart assessments to ascertain age at onset and lifetime illness course may impose limitations on generalizability in the absence of prospective data. Conclusions: Early onset of bipolar illness appears related to the development of rapid cycling and of comorbid substance abuse/dependence. The findings raise developmental implications for the pathogenesis of illness complexity and poor outcome states.