Longitudinal association of PTSD symptoms and self-reported physical functioning among Veterans

Background: Few longitudinal studies have investigated the potentially dynamic relationship between Posttraumatic Stress Disorder (PTSD) and physical functioning, and the number of follow-up timepoints have been limited. We evaluated whether PTSD symptoms predicted future physical functioning and vice versa using five assessments over four years. Methods: Data was used from a longitudinal cohort of 695 participants recruited from Veteran Affairs medical outpatient clinics who experienced a traumatic event. PTSD symptom severity was assessed annually with the PTSD Checklist (PCL). Physical functioning was measured with the 10-item subscale of the SF-36. An auto-regressive cross-lagged panel model was used to determine the temporal associations between PTSD and physical functioning, adjusting for age, sex, ethnicity, education and employment. Comorbidities and health behaviors were added to assess their roles in the relationship. Results: Greater PTSD symptom severity predicted worse physical functioning the following year (average beta=-0.10, P < 0.001), where a 10-point increase in PCL score predicted a 0.3-point decline in physical function score over one year. Similarly, better physical functioning also predicted reduced PTSD severity the following year, but to a smaller magnitude (average beta=-0.04, P=.003). The pattern of effects was similar after controlling for comorbidities and health behaviors. Limitations: Both primary variables relied on self-report, and generalizability may be limited by the mostly male Veteran sample. Conclusions: Our results support a bidirectional, but unequal, relationship between PTSD and physical functioning over time. They also highlight the importance of long-term control of PTSD symptoms in preventing functional decline.