Transdiagnostic Cognitive Behaviour Therapy (tCBT), an intervention designed to be applicable across multiple diagnoses, was introduced to improve limitations in traditional therapy such as cost and access to trained therapists. It has been established as an effective and efficacious treatment for anxiety disorders, though there has been little research focussed on the role of depression. The current study investigated the role of comorbid depression during tCBT for anxiety disorders in primary care settings as an outcome and a moderator of anxiety outcomes. Results of multi-level ANOVAs indicated no significant difference in anxiety outcomes regardless of whether there was a comorbid depression diagnosis in the tCBT condition, and that individuals with a comorbid depression diagnosis experienced significantly greater reduction in anxiety severity than those without. Depression symptom severity decreased to a significantly greater extent in the tCBT condition than in TAU when the outcome measure of Patient Health Questionnaire was utilised as the outcome measure, but this was not mirrored when the Clinician Severity Rating was utilised as the outcome measure. This study provides preliminary support for the effectiveness of Transdiagnostic Cognitive Behaviour therapy for those with both a principal anxiety disorder and comorbid depression in symptom reduction.
Keywords: Anxiety disorders; comorbid depression; effectivenes; randomized clinical trial.