Introduction
Posttraumatic stress disorder (PTSD) is a chronic and disabling psychological disorder that leads to significant impairment in interpersonal and work functioning.1 Despite the availability of several evidence-based treatments for PTSD the effectiveness of these treatments has yielded mixed results, especially in community settings (eg, ref 2). To address this heterogeneity in outcomes, there has been an increased focus on ‘personalized medicine’, with an emphasis on identifying predictors and treatment moderators that can help differentiate and understand differing treatment outcomes for individuals.3 This identification of pretreatment and moderating client characteristics that can predict differential responses to treatment is crucial as they can be leveraged to optimise treatment, especially for those with poorer outcomes.4
Several studies have focused on identifying client-level demographic predictors of different types of treatment outcome for PTSD, but with mixed results. For example, some studies have found that fixed demographic characteristics, such as sex, age, education level and marital status, did not predict treatment outcome (eg, ref 5) whereas others found significant treatment differential outcomes (eg, ref 6). Thus, the exploration of predictors of treatment response in PTSD has yielded mixed results. A similar pattern is present when identifying predictors of treatment dropout. A recent meta-analysis by Swift and Greenberg showed that despite client demographic variables having been explored most frequently as predictors, few led to consistent results related to dropout.7
The inconsistency in the pretreatment client-level predictors for both PTSD symptom improvement and dropout highlights the importance of looking at additional variables that may help understand the differential effectiveness of PTSD treatment and high dropout rates.2 For example, treatment language could be of potential significance for predicting treatment outcome and/or dropout. Previous research has shown that treatment language impacts the actual delivery of treatment, with clients seen in community settings often reporting difficulties in treatment related to language barriers.8 Furthermore, there is growing evidence for the need and importance of adapting evidence-based treatments (EBTs), such as cognitive processing therapy (CPT),9 to address these language-related treatment limitations when delivered in these settings (eg, ref 10).
Client’s barriers to treatment seeking could be another significant client-level predictor of PTSD treatment outcome and dropout. For example, different types of barriers to seeking treatment, such as stigma, logistical and financial concerns, and attitudes towards treatment, have been shown to impact clients’ treatment utilisation (eg, ref 11), and there is preliminary evidence suggesting that they may even impact treatment outcomes. For example, shame and guilt at pretreatment have been shown to lead to less decrease in PTSD symptoms over the course of therapy (eg, ref 12), whereas stigma, logistical and financial concerns, and negative attitudes towards treatment increased the likelihood of dropout from treatment (eg, ref 13).
Previous studies also suggest exploring baseline PTSD severity as a significant predictor for treatment outcome and dropout. Baseline PTSD severity has been associated with poorer quality of life and there is evidence to support the synchronous change in PTSD symptoms, quality of life and employment gains during treatment.14 The few studies that have started to understand the relationship between baseline PTSD severity and treatment outcome have yielded mixed results (eg, ref 5 15). Accordingly, it is important to assess whether these additional client-level characteristic variables may predict treatment outcome and dropout in PTSD.
In addition to exploring more reliable predictors of treatment outcome, variables that predict treatment engagement in community settings are also important. A recent study by Gutner et al found a high degree of variability in clients’ frequency and consistency of treatment attendance in a trauma clinic that served the community, and their results showed that more frequent and consistent session attendance was associated with greater PTSD symptom reduction, highlighting the importance of further exploring these treatment moderators among diverse samples of trauma survivors.16 Furthermore, Imel et al found that greater number of sessions attended predicted client’s treatment dropout in PTSD.17 Despite the importance of attendance as a treatment moderator, few studies to date have explored client-level predictors of attendance and other types of assessments of treatment engagement. For example, stigma, but not clients’ attitudes towards treatment, has been shown to be significantly related to number of sessions received.18 Lower quality of life scores have been shown to be associated with lower treatment attendance in clients with PTSD.19 Thus, it is imperative to explore client-level predictors that impact the various ways that clients seen in community settings engage in treatment.
The primary aim of this study is to build on the existing literature with two goals: (1) explore additional client-level predictors of treatment outcome and dropout in PTSD treatment that extend beyond client demographics, and (2) identify client-level predictors of treatment engagement. The results of the present study would aid researchers and clinicians in optimising treatment for PTSD by helping identify clients with differing treatment outcomes.