A randomised controlled trial to compare clinical and cost-effectiveness of an online parent-led treatment for child anxiety problems with usual care in the context of COVID-19 delivered in Child and Adolescent Mental Health Services in the UK (Co-CAT): a study protocol for a randomised controlled trial.

Background: In the context of COVID-19, NHS Child and Adolescent Mental Health Services (CAMHS) and other children's mental health services have faced major challenges in providing psychological treatments that (i) work when delivered remotely and (ii) can be delivered efficiently to manage increases in referrals as social distancing measures have been relaxed. Anxiety problems are a common reason for referral to CAMHS, children with pre-existing anxiety problems are particularly vulnerable in the context of COVID-19, and there were concerns about increases in childhood anxiety as schools reopened. The proposed research will evaluate the clinical and cost-effectiveness of a brief online parent-led cognitive behavioural treatment (CBT) delivered by the OSI (Online Support and Intervention for child anxiety) platform with remote support from a CAMHS therapist compared to 'COVID-19 treatment as usual' (C-TAU) in CAMHS and other children's mental health services throughout the COVID-19 pandemic.

Methods: We will conduct a two-arm, multi-site, randomised controlled non-inferiority trial to evaluate the clinical and cost-effectiveness of OSI with therapist support compared to CAMHS and other child mental health services 'COVID-19 treatment as usual' (C-TAU) during the COVID-19 outbreak and to explore parent and therapists' experiences.

Discussion: If non-inferiority is shown, the research will provide (1) a solution for efficient psychological treatment for child anxiety disorders while social distancing (for the COVID-19 context and future pandemics); (2) an efficient means of treatment delivery as 'normal service' resumes to enable CAMHS to cope with the anticipated increase in referrals; and (3) a demonstration of rapid, high-quality evaluation and application of online interventions within NHS CAMHS to drive forward much-needed further digital innovation and evaluation in CAMHS settings. The primary beneficiaries will be children with anxiety disorders and their families, NHS CAMHS teams, and commissioners who will access a potentially effective, cost-effective, and efficient treatment for child anxiety problems.

Trial Registration: ISRCTN ISRCTN12890382 . Registered prospectively on 23 October 2020.