Untangling the psychiatric comorbidity of posttraumatic stress disorder in a sample of flood survivors.

This report empirically examines multiple explanations for the high rates of psychiatric comorbidity seen with posttraumatic stress disorder (PTSD). One hundred sixty-two St. Louis area survivors of the 1993 Great Midwest Floods were interviewed a few months after the flood subsided using the Diagnostic Interview Schedule (DIS) and its Disaster Supplement to assess psychiatric history relative to PTSD and five other psychiatric disorders. Thirty-five subjects (23%) met criteria for PTSD related to the flood. PTSD was frequently comorbid with other disorders. Seventeen subjects (10%) developed a new, non-PTSD psychiatric disorder after the flood. New non-PTSD disorders were rare in the absence of PTSD symptoms. Though prior psychiatric history was predictive of developing PTSD, no support was found that prior psychiatric history contributed to PTSD through social vulnerability. Thus, support was found for a model in which PTSD contributes to the development of other disorders following trauma, whereas no evidence was found to suggest that comorbid disorders develop independently of PTSD following trauma, or that comorbidity was due to symptom overlap among disorders. The lack of support for models in which psychosocial resources mediate the effect of psychiatric history on the development of PTSD indirectly confirms models of physiological vulnerability to PTSD development.