Impact of Psychiatric Comorbidity on Mortality in Veterans with Type 2 Diabetes

Background: Particular psychiatric disorders, such as depression, have a significant and negative effect on diabetes outcomes. However, we know very little about the impact of other psychiatric disorders, and of the effect of multiple psychiatric comorbidities, on the clinical course of diabetes. As such, the present study examined the impact of a wide range of psychiatric comorbidities on all-cause mortality in individuals with type 2 diabetes. Methods: Retrospective follow-up was conducted of 15,065 veterans with type 2 diabetes enrolled in hospital care between 1997 and 2006. Clinical diagnoses from patient records were used to construct four psychiatric disorder scales: internalizing (i.e., depression and anxiety); externalizing (i.e., alcohol and drug abuse); psychotic; and bipolar. Longitudinal relationships were examined between these scales and mortality using Cox regression. Results: Only externalizing disorders were significantly associated with mortality: hazard ratio = 1.22 (95% confidence interval = 1.02-1.47). In other words, each additional diagnosed externalizing disorder increased an individual's chance of dying over the follow-up period by 22%. This association remained significant when demographics and medical comorbidities were statistically controlled, but was rendered nonsignificant when medication adherence was introduced to the regression model. Conclusions: The results provide evidence that among individuals with diabetes, alcohol and drug abuse/dependence have a significant impact on mortality. This increased risk of mortality may have been due to the association between psychiatric disorders and adherence to antidiabetes medications observed in the present study. Individuals with co-occurring diabetes and alcohol or drug abuse should be targeted for intensive interventions given their acute increased risk of mortality.