Sequential Temporal Dependencies in Associations Between Symptoms of Depression and Posttraumatic Stress Disorder: An Application of Bivariate Latent Difference Score Structural Equation Modeling

Abstract

Depression and posttraumatic stress disorder (PTSD) are highly comorbid conditions that may arise following exposure to psychological trauma. This study examined their temporal sequencing and mutual influence using bivariate latent difference score structural equation modeling. Longitudinal data from 182 emergency room patients revealed level of depression symptom severity to be positively associated with changes in PTSD intrusion, avoidance, and hyperarousal over 3 time intervals, beginning shortly after the traumatic event. Higher scores on depression anticipated increases (or worsening) in PTSD symptom severity. The pattern of influence from PTSD symptom severity to change in depression symptom severity simply followed the general trend toward health and well-being. Results are discussed in terms of the dynamic interplay and associated mechanisms of posttrauma depression and PTSD symptom severity.

Notes

¹Whereas BDI and IES-R evaluations were a part of all assessment occasions, the CAPS was relegated to only the last two assessment occasions because it requires symptom duration of 1 month and the first assessment was targeted at 1 week following trauma. This situation was readily accommodated by incorporating a missing variable placeholder (McArdle & Woodcock, 1997).

²Mplus scripts for all bivariate latent difference score analyses in this article are available upon request from Daniel W. King.

³In addition to the four-factor representation of the structure of PTSD used in this article, an alternative four-factor structure was proposed by Simms et al. (2002). In this alternative model, the intrusion and avoidance symptom clusters remain the same, but a subset of items from the hyperarousal cluster are shifted to the numbing cluster to form what Simms et al. called dysphoria and a truncated hyperarousal cluster. When bivariate latent difference score analyses were performed to examine associations between depression and these modified symptom clusters, the findings supported positive and significant depression to change in dysphoria cross-variable links; dysphoria to change in depression links were nonsignificant, as were the cross-variable associations between depression and the reduced hyperarousal cluster. Results of these supplemental analyses are available from Daniel W. King.

⁴We also considered the possibility of a model incorporating nonlinear change. In particular, we consulted Hamagami and McArdle's (2006) model of differences between differences intended to accommodate shifts in slopes to capture acceleration or nonlinear/quadratic trajectories in the data. We evaluated this latent acceleration approach for the depression and intrusion, depression and avoidance, and depression and hyperarousal associations. In each case, the latent acceleration model did not fit as well as the latent difference score model, and thus the latter model was preferred.