Substance use disorders and suicide attempts in bipolar subtypes

Abstract

Bipolar disorder (BD) is associated with high rates of suicide attempt and completion. Substance use disorders (SUD) have been identified as potent risk factors for suicidal behavior in BD. However, little is known concerning differences between BD subtypes with regard to SUD as a risk factor for suicidal behavior. We studied previous suicidal behavior in adults with a major depressive episode in context of BD type I (BD-I; N=96) or BD type II (BD-II; N=42), with and without history of SUD. Logistic regressions assessed the association between SUD and suicide attempt history by BD type, and exploratory analyses examined the effects of other clinical characteristics on these relationships. SUD were associated with suicide attempt in BD-I but not BD-II, an effect not attributable to sample size differences. The higher suicide attempt rate associated with alcoholism in BD-I was mostly explained by higher aggression scores, and earlier age of BD onset increased the likelihood that alcohol use disorder would be associated with suicide attempt(s). The higher suicide attempt rate associated with other drug use disorders in BD-I was collectively explained by higher impulsivity, hostility, and aggression scores. The presence of both alcohol and drug use disorders increased odds of a history of suicide attempt in a multiplicative fashion: 97% of BD-I who had both co-morbid drug and alcohol use disorders had made a suicide attempt. A critical next question is how to target SUD and aggressive traits for prevention of suicidal behavior in BD-I.

Figure 1. Putative Mediators and Moderators of the Impact of Substance Use Disorders on Suicide Attempt in Bipolar I Disorder

Hypothetical schematic model of relationships between clinical characteristics found to be relevant to history of suicide attempt in Bipolar I Disorder. Factor 1, resulting from a principal component analysis, explains 69% of the variance among the highly correlated variables impulsivity, hostility, and aggressivity.