Implications of psychiatric comorbidity among combat veterans.

Limited research exists regarding the rates of and outcomes associated with psychiatric comorbidity among active duty military personnel. This study investigated the rates of comorbid psychiatric diagnoses among 81,720 U.S. Marines, and assessed the relationships between preexisting comorbid disorders and risk of psychiatric hospitalizations and attrition from service. The study used medical, deployment, and personnel records for all Marines who enlisted between 2002 and 2005. The baseline rate of comorbidity was 1.3% for Marines who deployed during the first term of service, and 6.3% for Marines who did not deploy. The most common baseline comorbidity among deployed Marines was mood disorders with anxiety disorders, and mood and adjustment disorders among nondeployed Marines. Logistic regression analyses revealed Marines with comorbid diagnoses before deployment were over three times more likely to attrite (odds ratio = 3.4, p < 0.001) and over five times more likely to be hospitalized for psychiatric symptoms (odds ratio = 5.1, p < 0.001) following deployment than those with no diagnoses. Similar patterns emerged among nondeployers. Outcomes associated with comorbid conditions were substantially worse than outcomes for single conditions. These findings demonstrate that Marines with a history of comorbid psychiatric diagnoses are at a much greater risk for adverse outcomes, specifically attrition from the military and psychiatric hospitalization.