Effectiveness and cost-effectiveness of a fully self-guided internet-based intervention for sub-clinical social anxiety symptoms: Protocol for a randomised controlled trial

Design and objective: This paper describes the protocol for a large-scale pragmatic, randomised controlled trial and economic evaluation to investigate the effectiveness and cost-effectiveness of the self-directed E-Couch social anxiety module versus a waiting list control condition, for reducing sub-clinical social anxiety symptoms in the general population. Study population: Community-based adults (aged 18þ) with social anxiety symptoms that do not meet the criteria for social anxiety disorder recruited via a direct-to-consumer advertisement on national websites. Intervention and control: Intervention is the self-guided E-Couch social anxiety module. Control group participants are placed on a waiting list to receive the intervention at the end of the trial. Both groups receive email and text message reminders. Outcome measures: The primary outcome will be change in self-reported social anxiety score using the Social Phobia Inventory (SPIN). Secondary outcomes will be the changes in the following self-report measures: Brief Fear of Negative Evaluation scale (BFNE-S); depression (CES-D); mental wellbeing (SWEMWEBS); health status (SF36); use of health services; safety events; and adherence, retention, and attrition rates. All measures will be administered at baseline, 6 weeks, and 3, 6 and 12 months. Analysis: A mixed effects model will be used to analyse the effect of the intervention on the primary and secondary outcomes (intention to treat analysis). Secondary analyses will explore moderators and mediators of effect. A prospective economic evaluation, conducted from a NHS and social care perspective, will provide estimates of cost utility and costeffectiveness. An interview study will be conducted with 20 participants to explore issues including acceptability, adherence, retention and attrition. Trial registration numbers: NCT02451878 and ISRCTN15819951