Relations between PTSD and depression symptom clusters in samples differentiated by PTSD diagnostic status.

Co-occurring posttraumatic stress disorder (PTSD) and depression following traumatic experiences are cumulatively associated with functional impairment. To examine mechanisms for the PTSD-depression comorbidity, we investigated their cluster-level associations. Using data obtained from Amazon's Mechanical Turk platform, 368 trauma-exposed participants were split into two subsamples: those with (n = 163) and without (n = 185) probable PTSD. In both subsamples, confirmatory factor analyses indicated an optimal seven-factor PTSD Hybrid Model. Results of Wald tests of parameter constraints indicated that, in both subsamples, PTSD's dysphoric arousal cluster strongly related to somatic depression compared to all/most other PTSD Hybrid Model clusters. Additionally, in both subsamples, PTSD's negative affect, externalizing behaviors, and anhedonia clusters each strongly related to non-somatic depression compared to PTSD's anxious arousal cluster. Our results indicated that PTSD's dysphoric arousal symptoms mainly accounted for PTSD's shared variance with somatic depression, while the negative alterations in cognitions and mood (NACM)/dysphoria and arousal symptoms (primarily externalizing behaviours) mainly accounted for PTSD's shared variance with non-somatic depression. Our findings have implications for the discussion on PTSD's specific/non-specific clusters tied to diagnostic modifications, for understanding mechanisms underlying PTSD-depression comorbidity, and for the use of transdiagnostic and multi-component treatment protocols for PTSD-depression symptoms.