Challenging the conclusion that lower preinduction cognitive ability increases risk for combat-related post-traumatic stress disorder in 2,375 combat-exposed, Vietnam War veterans.

OBJECTIVE: Among U.S. Vietnam War veterans, we assessed whether preinduction cognitive abilities were associated with the risk of developing combat-related post-traumatic stress disorder (PTSD).
METHODS: The sample included 2,375 single-term, enlisted, male, Army, Vietnam War veterans who reported exposure to combat during the war. There were two measures of cognitive abilities obtained before military induction, the Armed Forces Qualification Test and the General Technical Examination. Associations of ability with current and lifetime diagnoses of Diagnostic and Statistical Manual of Mental Disorders, Third Edition Revised, combat-related PTSD were assessed. An index was used to grade the severity of combat exposure.
RESULTS: Among low-combat exposure veterans, higher preinduction cognitive abilities decreased the risk for lifetime, Diagnostic and Statistical Manual of Mental Disorders, Third Edition Revised, combat-related PTSD. For veterans with higher levels of combat exposure, higher scores for preinduction cognitive abilities had no effect on reducing the risk for lifetime diagnosis of combat-related PTSD. For a current diagnosis of combat-related PTSD, approximately 20 years after the stressful life events, preinduction cognitive abilities had no effect on the rates of combat-related PTSD.
CONCLUSIONS: We found significant interactions between preinduction cognitive abilities and severity of combat exposure for the lifetime diagnosis of combat-related PTSD among Army Vietnam War veterans. High levels of combat exposure are likely to exhaust intellectual resources available for coping with stressful life events. Lower scores for cognitive abilities are not uniformly disadvantageous, and this should be considered by military manpower policymakers.