The relationship between PTSD factors and depression in a chronically homeless sample

The relationship between post-traumatic stress disorder (PTSD) and major depressive disorder (MDD) is the subject of ongoing inquiry. Homeless adults with psychiatric illnesses are at risk for comorbid PTSD and MDD. However, the factor structures of commonly used screening tools for PTSD (PCL-5) and MDD (PHQ-9), and their interrelationships, have not been widely investigated in this population. The present article tests the factor structure of the PCL-5 and PHQ-9 in a sample of chronically homeless adults who reported lifetime trauma exposure and were enrolled into intensive community mental health services (N = 197). Confirmatory factor analysis was used to test six models of PTSD and four models of depression, although more complex models produced indefinite covariance matrices. The four-factor Dysphoria Model of PTSD and a two-factor model of MDD were considered the best models in this sample. Regression analyses tested the variance between PTSD and MDD symptom clusters. The PTSD dysphoria factor explained the most variance in depressive symptoms. Reexperiencing, avoidance, and arousal symptoms capture phenomena unique to the experience of PTSD among this psychiatric sample. These findings have implications for conceptualizing the underlying structures of PTSD and MDD among a moderately depressed sample of homeless adults with psychiatric illnesses.