Psychological inflexibility predicts PTSD symptom severity in war veterans after accounting for established PTSD risk factors and personality.

Objective and Method: Numerous risk factors for posttraumatic stress disorder (PTSD) have been identified; however, many do not inform treatment. Psychological inflexibility is a modifiable factor that can be targeted in psychological treatment. This study examined whether higher levels of psychological inflexibility predicted unique variance in PTSD symptom severity at 1-year follow-up in 236 U.S. veterans of the wars in Iraq in Afghanistan after accounting for the strongest known risk factors for PTSD. PTSD symptom severity was assessed using the Clinician Administered PTSD Scale. Results: In hierarchical regression analyses, higher baseline psychological inflexibility predicted unique variance in 1-year PTSD symptom severity (p < .001, medium effect) after accounting for the strongest predictors, including: serving in the Army, rank, trauma severity, perceived threat, peritraumatic dissociation, recent life stress, and social support. Psychological inflexibility remained a significant predictor of unique variance in 1-year PTSD symptom severity after accounting for all other predictors and personality factors (neuroticism, extroversion, openness to experience, agreeableness, and conscientiousness; p < .001, small effect) and after accounting for all other predictors, personality factors, and baseline PTSD avoidance symptoms (p < .001; small effect). Conclusions: Findings indicate a key unique association between psychological inflexibility and PTSD symptom severity over time that is not attributable to overlap with personality or PTSD avoidance symptoms. Additional research on psychological inflexibility in the development and maintenance of PTSD is warranted, as well as whether increasing psychological flexibility leads to reductions in PTSD symptoms and improved psychosocial functioning.