Do Unified Protocol modules exert general or unique effects on anxiety, depression, and transdiagnostic targets?

Several transdiagnostic cognitive-behavior therapies include multiple treatment components. However, it is unclear whether some components are more efficacious than others at reducing symptoms or whether these components uniquely influence their putative mechanism of change. Participants (N = 70; M_age = 33.7; 67.1% female, 74.3% White) with a primary anxiety or depressive disorder were randomized to one of three standard or personalized sequences of core Unified Protocol modules. Using hierarchical linear modeling, we tested (a) whether the average session-to-session change in anxiety and depression differed between modules and (b) whether the average session-to-session change in the putative mechanism of each module differed between modules. All modules led to similar changes in anxiety, but Confronting Physical Sensations led to significantly less change in depression than other modules. There were no significant differences among modules predicting putative mechanisms of change, although there was a trend for Mindful Emotion Awareness to predict greater improvements in mindfulness than Understanding Emotions. Consistent with its transdiagnostic nature, UP modules may exert similar effects on anxiety and putative mechanisms of change, although interoceptive exposures may be less impactful for changing depressive symptoms and the mindfulness module may promote relatively specific improvements in mindfulness.