Factors influencing the efficacy of an online behavioural intervention for children and young people with tics: Process evaluation of a randomised controlled trial

The Online Remote Behavioural Intervention for Tics (ORBIT) trial found that an internet-delivered, therapist-supported, and parent-assisted Exposure and Response Prevention (ERP) intervention reduced tic severity and improved clinical outcomes. This process evaluation aimed to explore mechanisms of impact and factors influencing efficacy. Participants were 112 children with a tic disorder and their parents randomised to the active intervention arm of the ORBIT trial. Child engagement was assessed by usage metrics and parent engagement by chapter completion. Experiences of the digital intervention were explored by semi-structured interviews. Outcomes (3-months post randomisation) were change in tic severity and overall clinical improvement. Tic severity reduced from baseline to 3-month follow-up and 36% were rated as much improved clinically. Greater tic severity at baseline predicted reduction in tic severity. Parental engagement was the only independent predictor of clinical improvement. There were no statistically significant mediators or moderators of the relationship between level of child engagement and outcome. From the qualitative findings, child participants appreciated working together with parents on the intervention and participants found the intervention engaging. ORBIT may be an effective and acceptable intervention for children and young people with tic disorders, with parental engagement being a key factor in successful outcomes.