Relationship between intelligence and posttraumatic stress disorder in veterans

Abstract

ObjectiveEvaluate the relationships between posttraumatic stress disorder (PTSD) and measures of intelligence in veterans. MethodVeterans (N = 338) who deployed to Iraq and/or Afghanistan were recruited for a VA study on primary blast exposure. PTSD was evaluated using the Clinician Administered PTSD Scale, 5th edition (CAPS-5) and the PTSD Checklist-5. Intelligence was measured using the Wechsler Adult Intelligence Scale, 4th edition and the Test of Premorbid Functioning (TOPF). Validity was assessed with the Medical Symptom Validity Test, b Test, and Structured Inventory of Malingered Symptomatology. Differences in Intelligence Quotient (IQ) estimates between individuals with and without PTSD were evaluated with t-tests. Correlations evaluated associations between symptom burden and intelligence. ResultsOf the seven IQ measures, only the Full Scale IQ score and TOPF Equated scores were significantly lower (but not abnormal) in the lifetime PTSD group. Moreover, these relationships were no longer significant when accounting for multiple comparisons, and symptom/performance validity appeared to better account for those relationships. Current symptom distress was weakly related to several outcomes, but not when using CAPS-5 measures. Neither lifetime nor current PTSD diagnoses were associated with significantly lower IQ scores. ConclusionsThis study did not support prior conclusions that low IQ is a risk factor for developing PTSD. This discrepancy is likely due to the use of ability and symptom validity checks, and sample characteristics (e.g., education). Future research should further evaluate the relationship of symptom distress on intellectual outcomes in combat veteran samples.