Within-person changes in aversive reactivity predict session-to-session reductions in anxiety and depression in the unified protocol.

The Unified Protocol (UP) theoretically leads to reductions in emotional disorder symptoms by reducing aversive reactions to emotions. However, aversive reactions can take many forms (e.g., non-acceptance, behavioral avoidance). We examined if (1) multiple aspects of aversive reactivity predicted session-to-session changes in anxiety and depression in the UP, (2) these aspects reflected a single latent construct, and (3) changes in this latent construct predicted changes in anxiety and depression. Participants (= 70,  = 33.74, 67.1% female, 74.3% white) completed six sessions of UP modules and measures of aversive reactivity, anxiety, and depression before each session. We used hierarchical linear modeling and random-intercept cross-lagged panel models to test aspects of aversive reactivity and a latent factor of aversive reactivity, respectively, as predictors of session-to-session changes in anxiety and depression. Within-person improvements in four of five aspects of aversive reactivity predicted decreases in anxiety, and improvements in two aspects predicted decreases in depression. However, within-person improvements in latent aversive reactivity predicted decreases in anxiety at five sessions and in depression across all sessions. These results add to the growing literature highlighting the role of aversive reactivity as a potential transdiagnostic process involved in improvements in emotional disorder symptoms during treatment.