Exploring trajectories in transdiagnostic behavior therapy.

Transdiagnostic treatments have been designed to target common processes for clusters of disorders. One such treatment, transdiagnostic behavior therapy (TBT), targets avoidance across emotional disorders, including posttraumatic stress disorder (PTSD), depressive disorders, and anxiety disorders, and has demonstrated efficacy in randomized controlled trials. The current study was designed to examine whether distinct treatment trajectories would emerge in a sample of 112 veterans receiving TBT and whether diagnostic comorbidity, baseline levels of several transdiagnostic risk factors, or treatment engagement influence trajectory membership. Growth mixture modeling revealed three distinct trajectories across depression, ds = 0.55-1.09; PTSD ds = -0.07-1.43; and panic disorder symptoms, ds = -0.13-1.09. Notably, for PTSD and panic disorder symptoms, separate classes for responders and nonresponders emerged among participants with high baseline symptom levels. Findings for the risk factors suggested that PTSD and panic nonresponders evidenced significantly higher behavioral avoidance at baseline and reduced engagement in treatment procedures and homework completion compared to responders. Together, the findings provide additional support for the use of TBT in the treatment of emotional disorders, including PTSD. Potential adaptations are discussed for patients with significantly elevated behavioral avoidance to improve treatment engagement and related outcomes.