Background The aim of the current study was to compare the Unified Protocol for Transdiagnostic Treatment of Emotional Disorders (UP) with and without transcranial direct current stimulation (tDCS) in individuals suffering from generalized anxiety disorder (GAD) and comorbid depression. Methods A total of 43 individuals diagnosed with GAD and comorbid depression enrolled in a randomized controlled trial (IRCT20140929019334N1). Participants were randomly assigned to three groups including UP with tDCS (UP+tDCS; n=15), UP alone (UP; n=13) or wait-list control (n=15). GAD and depression symptoms, worry severity, anxiety sensitivity, and intolerance of uncertainty were assessed at baseline, post-treatment and 3-month follow-up. Results Treatment with both UP+tDCS and UP alone resulted in significant lower ratings across all measures relative to wait-list controls at post-treatment and 3-month follow-up (all p-values <.001). UP+tDCS showed significantly greater reductions in anxiety (p = .001 post-treatment; p=.003 follow-up), worry (p=.001 post-treatment; p=.002 follow-up), and anxiety sensitivity (p=.003 post-treatment; p=.002 follow-up) relative to UP alone. Limitations The present study had some limitations. First, the sample size was low. Another limitation was the use of a short-term follow-up. Conclusions These results suggest augmenting UP treatment with tDCS may be an efficacious strategy to improve treatment outcomes in GAD with comorbid depression. Trial registration reference is IRCT20140929019334N1 (see https://irct.ir/trial/27988).

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