BACKGROUND: Posttraumatic stress disorder (PTSD) and depression are highly comorbid and intercorrelated. Yet little research has examined the underlying processes explaining their interrelationship. METHOD: In the present survey study, the investigators assessed the combined symptom structure of PTSD and depression symptoms, to examine shared, underlying psychopathological processes. Participants included 740 Canadian military veterans from a national, epidemiological survey, previously deployed on peacekeeping missions and administered the PTSD Checklist and Center for Epidemiological Studies-Depression Scale (CES-D). RESULTS: An eight-factor PTSD/depression model fit adequately. In analyses validating the structure, PTSD's dysphoria factor was more related to depressive affect than to several other PTSD and depression factors. Somatic problems were more related to dysphoria than to other PTSD factors. LIMITATIONS: Only military veterans were sampled, and without the use of structured diagnostic interviews. CONCLUSIONS: Results highlight a set of interrelationships that PTSD's dysphoria factor shares with specific depression factors, shedding light on the underlying psychopathology of PTSD that emphasizes dysphoric mood.
Elhai et al. (2011) studied this question.