404: Personal Data Not Found — Efficacy of Anonymous Internet-Based Self-Help for Social Anxiety in a Partially Randomized Patient Preference Trial

Background:Internet-based interventions can improve access to evidence-based treatments. However, concerns about privacy and data security remain barriers to their adoption. Designing interventions that allow anonymous use may reduce these barriers, but whether anonymity affects treatment efficacy remains unclear. Objective: This study compared clinical outcomes of an anonymous internet-based self-help intervention for social anxiety to a conventional non-anonymous version and investigated whether participants’ preferences regarding anonymity influenced treatment outcomes. Methods: In this partially randomized patient preference trial, 452 adults with clinically relevant social anxiety symptoms were assigned by randomization or preference to an anonymous or non-anonymous 8-week unguided cognitive behavioral self-help program. Assessments were conducted at baseline, post-treatment, and 24-week follow-up. The primary outcome was social anxiety severity. Mixed-effects models were used to evaluate changes over time and differences between program versions.ResultsParticipants showed significant reductions in social anxiety symptoms over time with medium to large within-group effect sizes (d = -0.81 to -0.62). No significant superiority of the non-anonymous version was observed in the randomized or preference arms. Secondary outcomes including depressive symptoms, quality of life, and internalized stigma also improved. Effects were maintained at follow-up and did not differ by allocation method. Further exploratory analyses did not provide robust evidence of outcome differences by preference match.DiscussionThe anonymous intervention was not outperformed by the conventional non-anonymous program. These findings provide preliminary evidence that anonymity need not compromise intervention efficacy and strong privacy protections may help address privacy-related barriers.