Effect of comorbid alcohol and drug use disorders on premature death among unipolar and bipolar disorder decedents in the United States, 1999 to 2006

Objective: The aim of this study was to quantify the effect of comorbid alcohol and drug use disorders on premature death, as reflected by the manner of death (suicide and other unnatural death versus natural death) and the age at death, among decedents with unipolar and bipolar disorders.

Methods: This study is based on the US Multiple Cause of Death public-use data files for 1999 to 2006. Secondary data analysis was conducted comparing decedents with unipolar/bipolar disorders and decedents with all other causes of death, based on the death records of 19,052,468 decedents in the Multiple Cause of Death data files who died at 15 years and older. Poisson regression models were used to derive prevalence ratios to assess the effect of comorbid substance use disorders (SUD) on the risks for being an unnatural death among mood disorder deaths. Multiple-cause life table analysis and mean age at death were used to quantify the effect of comorbid SUDs on premature mortality among mood disorder deaths.

Results: Prevalence of comorbid SUDs was higher among unipolar and bipolar disorder deaths than that among all other deaths. Among unipolar and bipolar disorder deaths, comorbid SUDs were associated with elevated risks for suicide and other unnatural death in both men and women (prevalence ratios ranging 1.49-9.46, P < .05). They also were associated with reductions in mean ages at death (ranging 11.7-33.8 years, P < .05). In general, these effects were much stronger for drug use disorders than for alcohol use disorders. Both SUDs had stronger effects on suicide among women, whereas their effects on other unnatural deaths were stronger among men.

Conclusions: This study is among the first to provide population mortality-based evidence to further establish comorbid SUD as one of the key risk factors for premature death among individuals with unipolar or bipolar disorders in the United States. Clinicians need to be aware of the potentially lethal risk associated with these comorbid conditions.