Clinical effectiveness and cost-effectiveness of Internet- vs. group-based cognitive behavior therapy for social anxiety disorder: 4-year follow-up of a randomized trial.

Social anxiety disorder (SAD) is common, debilitating and associated with high societal costs. The disorder can be effectively treated with Internet-based cognitive behavior therapy (ICBT), but no previous study has investigated the long-term clinical or health economic effects of ICBT for SAD in comparison to an evidence-based control treatment. The aim of the study was to investigate the clinical effectiveness and cost-effectiveness of ICBT compared to cognitive behavioral group therapy (CBGT) four years post-treatment. We conducted a 4-year follow-up study of participants who had received ICBT or CBGT for SAD within the context of a randomized controlled non-inferiority trial. The cost-effectiveness analyses were conducted taking a societal perspective. Participants in both treatment groups made large improvements from baseline to 4-year follow-up on the primary outcome measure (d = 1.34-1.48) and the 95% CI of the mean difference on the primary outcome was well within the non-inferiority margin. ICBT and CBGT were similarly cost-effective and both groups reduced their indirect costs. We conclude that ICBT for SAD yields large sustainable effects and is at least as long-term effective as CBGT. Intervention costs of both treatments are offset by net societal cost reductions in a short time.