Efficacy of digital cognitive behavioural therapy for symptoms of generalised anxiety disorder: a study protocol for a randomised controlled trial

Background Generalised anxiety disorder (GAD) is a chronic and disabling condition with considerable personal and economic impact. Cognitive behavioural therapy (CBT) is a recommended psychological therapy for GAD; however, there are substantial barriers to accessing treatment. Digital CBT, in particular smartphone-delivered CBT, has the potential to improve accessibility and increase dissemination of CBT. Despite the emerging evidence of smartphone-based psychological interventions for reducing anxiety, effect size scores are typically smaller than in-person interventions, and there is a lack of research assessing the efficacy of smartphone-delivered digital interventions specifically for GAD. Methods In the DeLTA trial (DigitaL Therapy for Anxiety), we plan to conduct a parallel-group superiority randomised controlled trial examining the efficacy of a novel smartphone-based digital CBT intervention for GAD compared to a waitlist control. We aim to recruit 242 adults (aged 18 years or above) with moderate-to-severe symptoms of GAD. This trial will be conducted entirely online and will involve assessments at baseline (week 0; immediately preceding randomisation), mid-intervention (week 3), post-intervention (week 6; primary end point) and follow-up (week 10). The primary objective is to evaluate the efficacy of the intervention on GAD symptom severity compared to a waitlist control at post-intervention. Secondary objectives are to examine between-group effects on GAD at follow-up, and to examine the following secondary outcomes at both post-intervention and follow-up: 1) worry; 2) depressive symptoms; 3) wellbeing; 4) quality of life; and 5) sleep difficulty. Discussion This trial will report findings on the initial efficacy of a novel digital CBT intervention for GAD. Results have the potential to contribute towards the evidence base for digital CBT for GAD and increase the dissemination of CBT.