Transdiagnostic Processes as Mediators of Change in an Internet-Delivered Intervention Based on the Unified Protocol

Background Transdiagnostic treatments target shared mechanisms between disorders to facilitate change across diagnoses. The Unified Protocol (UP) aims at changing dysfunctional reactions towards emotions by increasing mindful emotion awareness and cognitive flexibility, as well as decreasing anxiety sensitivity and emotion avoidance. Method We investigated whether these transdiagnostic processes were malleable by treatment and mediated the relationship between treatment and outcome in an internet-delivered adaptation of the UP. N = 129 participants with mixed anxiety, depressive, and somatic symptom disorders were randomized to treatment or waitlist. Results The treatment yielded significant changes in all transdiagnostic processes over time in comparison to a waitlist condition. In separate mediator models, significant mediating effects were found for mindfulness, cognitive flexibility, behavioral activation, and experiential avoidance. When all mediators were combined in a multiple mediator model, the indirect effects through mindfulness and cognitive flexibility emerged as significant. Conclusion These findings add to the growing body of research on transdiagnostic processes as mediators of change and emphasize mindfulness and cognitive flexibility as a transdiagnostic treatment target. However, these results should be interpreted cautiously, as temporal precedence could not be established.