Within exposure-based trauma treatments for posttraumatic stress disorder (PTSD), imagery vividness during imaginal exposure of the traumatic memory is an understudied but potentially important predictor of treatment outcome. Further, to our knowledge, this relationship has only been studied in women to date, and never among individuals with PTSD and substance use disorders which could impact ability to produce vivid mental imagery and its impact. The current study investigated whether imagery vividness ratings during in-session exposure predicted post-treatment PTSD symptom severity in a sample of men and women with comorbid PTSD and substance use disorders, and also examined whether gender moderated this relationship. A sample of 71 participants who received an exposure-based trauma treatment were included in the analyses. PTSD symptom severity was assessed using both the Clinician Administered PTSD Scale (CAPS) and the Impact of Event Scale-Revised (IES-R). Results varied according to method of assessing PTSD symptom severity. Higher imagery vividness was associated with better treatment outcome when assessed by the CAPS, with vividness in later sessions relating more strongly to outcome than vividness in earlier sessions. With the IES-R, higher imagery vividness ratings predicted more favorable treatment outcome for men, but less favorable treatment outcomes for women. Findings are discussed in the context of using imagery vividness to maximize treatment outcomes and future research directions involving scientific replication.
Posttraumatic stress disorder (PTSD) is a debilitating psychological disorder that can develop following exposure to traumatic events, and is a prevalent public health concern (i.e., lifetime prevalence of 6.8%; NCS-R; Kessler, Berglund, Demler, Jin, & Merikangas, 2005) that is associated with a variety of problems. These include psychological comorbidity (e.g., depression, panic attacks, substance use), occupational impairment, and elevated health care costs (Hofmann et al., 2002, Kessler, 2000 and Walker et al., 2003). Several effective treatments for PTSD currently exist (see Foa, Keane, Friedman, & Cohen, 2008 for a review), including Prolonged Exposure (Foa, Hembree, & Rothbaum, 2007). Prolonged Exposure consists of several components typical of cognitive-behavioral treatments, including in vivo and imaginal exposure. In imaginal exposure, patients repeatedly recount their most distressing traumatic memory, while in vivo exposure involves gradual and systematic exposure to individualized trauma triggers (e.g., situations, objects).
We examined several research questions in the current analysis. We used a multilevel modeling approach in order to evaluate session-by-session and pre-to post-treatment change in SUDS, imagery vividness, and treatment outcome (the highest vividness rating within each session was identified as the primary independent variable). Multilevel modeling confers the advantage of providing robust statistical analyses with missing data (Field, 2009). In analyses that included random effects, an autoregressive error covariance matrix was defined, as residual error is likely to be correlated within individuals across time (Hox, 2010). While we included slope and intercept within participants as random effects in appropriate models, our primary focus was on the fixed effects of predictor variables. For treatment outcome variables, findings reflect multiple linear regression models that controlled for baseline levels of PTSD symptoms. Predictor variables were centered prior to analyses. We also examined the skewness of potential mediators and dependent variables prior to analyses. Vividness demonstrated a negative skew, which was corrected with a square root transformation.
