The development of Cognitive Behavioural Therapy (CBT) for chronic loneliness in children and young people: Protocol for a single-case experimental design.

Loneliness is a significant problem for young people and is associated with a range of physical and mental health difficulties. Meta-analyses have identified that interventions aimed at young people who report loneliness as their primary problem are lacking within the literature. In adults, the most effective interventions for loneliness are those which target the underlying maladaptive social cognitions. Therefore, we have developed a modular Cognitive Behavioural Therapy (CBT) intervention for children and young people. The aim of this study is to conduct a multiple baseline single-case experimental design (SCED) to assess the efficacy, feasibility and acceptability of this intervention. In total 6-8 11-18-year-olds and their families will be recruited. The design consists of AB+ post-intervention, where A is the baseline phase, B is the intervention phase and then a post-intervention phase. Participants will complete a baseline assessment, before being randomised to one of four different baseline lengths (12 days, 19 days, 26 days or 33 days). Participants will then complete an average of 12 sessions of CBT, with the aim being to reduce their feelings of loneliness. Participants will then complete a 12-day post-intervention phase. Participant loneliness will be repeatedly assessed throughout the three phases of the intervention using the Three-item Loneliness Scale, which will be the primary outcome. Secondary outcomes will be reliable and clinically meaningful change on the UCLA Loneliness Scale, Revised Child Anxiety and Depression Scale (RCADS) and Strengths and Difficulties Questionnaire (SDQ). Feasibility and participant satisfaction will also be assessed and reported. Trial registration: ClinicalTrails.gov trial registration number: NCT05149963 (Date registered: 07.12.2021). https://www.clinicaltrials.gov/ct2/show/NCT05149963?term=cbt&cond=loneliness&draw=2&rank=1.