Symptom Trajectories in Patients With Anxiety Disorders During Transdiagnostic Cognitive Behavioral Therapy.

Growing research confirms the efficacy of transdiagnostic cognitive behavioral psychotherapy, that is treatments applicable across multiple diagnoses within a disorder class or spectrum, by examining group-level changes from pre- to posttreatment. However, less is known about interindividual differences and dynamic changes during therapy. Understanding different symptom trajectories and their associations with treatment outcome would allow early detection of nonresponders and treatment adjustments. Using data from the treatment group of a randomized controlled trial, we aimed to investigate trajectories in transdiagnostic cognitive behavioral therapy (CBT) with the Unified Protocol (UP) in patients with anxiety disorders. Patients reported on demographics, clinical history, coping strategies, treatment motivation, and expectations before starting transdiagnostic CBT. Participants provided symptom ratings across 16 sessions of the UP as well as at posttreatment, 6-, and 12-month follow-up (N = 64, 71.9% female, age: M = 32.67, SD = 11.91). Using latent class growth analysis (LCGA), we identified symptom trajectory classes and tested whether these could be predicted from baseline data. We also examined associations between classes and treatment outcome, using multilevel modeling and reliable change indices (RCIs). LCGA revealed four distinct trajectory classes: low severity-improved (n = 21, 32.81%), high severity-improved (n = 19, 29.69%), high severity-stagnant (n = 12, 18.75%), and low severity-worsened (n = 12, 18.75%). Only the number of comorbidities emerged as a significant predictor of class, with patients in the high severity-stagnant group having more comorbidities. They also showed higher symptom severity at baseline, posttreatment, and follow-ups compared to other classes, despite clear improvement. Latent classes of symptom changes during transdiagnostic CBT can be distinguished and important pretreatment factors identified, informing treatment selection and personalization. Particularly patients with high initial burden and a higher number of comorbidities may require monitoring and adaptive treatment strategies, which should be explored in future studies. Trial Registration: ClinicalTrials.gov identifier: NCT03945617.