However, what isn't clearly known, however, is how PTSD relates to mood disorders and pain severity in chronic pain patients.

University of Michigan researchers examined the contribution of PTSD to the pain experience, functional disability and frequency of depressive symptoms. They studied 241 patients referred to the university hospital's pain rehabilitation program who reported their pain began after a traumatic injury. The subjects completed the McGill Pain Questionnaire and were administered the Pain Disability Index and the Post-traumatic Chronic Pain Test.

The study found PTSD and depression were significantly correlated and both disorders were associated with perceived disability attributed to chronic pain.

The study authors concluded that increased attention to treating PTSD as a primary focus in the rehabilitation of patients with chronic pain and co-morbid depression is important when prior treatment efforts for pain and depression have not been successful.