Suicide risk in bipolar patients: the role of co-morbid substance use disorders

Objective: Bipolar disorder is associated with a high frequency of both completed suicides and suicide attempts. The primary aim of this study was to identify clinical predictors of suicide attempts in subjects with bipolar disorder. Methods: We studied 336 subjects with a diagnosis of bipolar I, bipolar II, or schizoaffective disorder (bipolar type). The Structured Clinical Interview for DSM-IV (SCID-I) was administered and subsequently two expert psychiatrists established a diagnosis. Predictors of suicide attempts were examined in attempters and non-attempters. Results: The lifetime rate of suicide attempts for the entire sample was 25.6%. A lifetime co-morbid substance use disorder was a significant predictor of suicide attempts: bipolar subjects with co-morbid substance use disorders (SUD) had a 39.5% lifetime rate of attempted suicide, while those without had a 23.8% rate (odds ratio=2.09, 95% CI=1.03-4.21, chi(2)=4.33, df=1, p=0.037). Conclusions: Lifetime co-morbid SUD were associated with a higher rate of suicide attempts in patients with bipolar disorder. This relationship may have a genetic origin and/or be explained by severity of illness and trait impulsivity.