Birth‐cohort and dual diagnosis effects on age‐at‐onset in Brazilian patients with bipolar I disorder

Objective: Substance use disorders and birth‐cohort have been associated with an earlier onset in bipolar disorder (BD). This study aimed at evaluating the inter‐relations of these factors in age‐at‐onset in bipolar illness.Method: Two‐hundred and thirty patients with bipolar I disorder were cross‐sectionally evaluated. Patients were categorized into four age groups for analysis. Lifetime comorbidity and age‐at‐onset were derived from the Structured Clinical Interview for DSM‐IV.Results: There was a strong linear association between age group and age‐at‐onset. Lifetime alcohol and drug use disorders were also associated with age‐at‐onset. Illicit drug and alcohol use disorders and age group remained significant in the multivariate model. No interactions appeared.Conclusion: Both age group and dual diagnoses had strong and independent impacts on age‐at‐onset in out‐patients with BD. Substance abuse may be partly accountable for earlier symptom onset, but other features of BD in younger generations are still in need to be accounted for.

Birth‐cohort and dual diagnosis effects on age‐at‐onset in Brazilian patients with bipolar I disorder Journal Articles