High-intensity mindfulness and cognitive behavioral group therapy for social anxiety disorder: Preliminary efficacy.

Aim: Cost and probability biases are known to predict improvements in symptoms of social anxiety disorder (SAD). This study developed a high-intensity mindfulness and cognitive behavioral group therapy (M-CBT) program-comprising mindfulness training, psychoeducation, cognitive restructuring, exposure exercises, and group　sharing-designed to reduce these biases. The intervention was delivered in a group format, and its preliminary efficacy in patients with SAD was evaluated in a pilot single-arm trial. Methods: Patients (N = 10) diagnosed with SAD through a structured clinical interview participated in an eight-session M-CBT program. They completed a set of questionnaires assessing SAD symptoms, cost and probability biases, fear of negative evaluation, self-focused attention, depressive symptoms, subjective happiness, dispositional mindfulness, cognitive reappraisal, and suppression at pre-intervention, mid-intervention, post-intervention, and follow-up. Results: Analyses using linear mixed-effects models revealed that high-intensity M-CBT produced improvements in SAD symptoms, cost and probability biases, depressive symptoms, subjective happiness, dispositional mindfulness, and cognitive reappraisal (p < 0.05). The intervention also yielded significant reductions in cost and probability biases from pre- to post-treatment and at follow-up, with large effect sizes (cost bias: Cohen's d = 0.85-1.27; probability bias: d = 1.07-2.42). In contrast, the effect sizes for SAD symptoms were moderate (d = 0.57-0.67). Conclusions: These findings suggest that high-intensity M-CBT can alleviate SAD symptoms and reduce cost and probability biases. Moreover, delivering M-CBT in a high-intensity format appears to be effective for individuals with SAD. Future randomized-controlled trials are warranted to more rigorously confirm these effects.