Cognitive-behavioural therapy for anorexia nervosa (CBT-AN-20): feasibility, acceptability, and preliminary effectiveness

This study examined the feasibility, acceptability, and preliminary effectiveness of CBT-AN-20, a novel 20-session outpatient treatment for anorexia nervosa. A longitudinal case-series study (preregistration: https://doi.org/10.17605/OSF.IO/S2WNY) conducted in adult outpatient eating disorder services assessed CBT-AN-20's feasibility (eligible patients recruited who started treatment, retention, attendance), acceptability (suitability/confidence), and effectiveness (recovery rates, reliable change, outcome measures). Completer analyses indicated high feasibility (recruitment: 84.72%) and moderate-to-high acceptability (retention: 57.38%; session attendance: 84%). Both completer and Intention to Treat (ITT) analyses showed similar improvements in weight, eating pathology, anxiety and depression, all with large effect sizes. Pre-post treatment recovery rates for weight (64.29%) were broadly comparable to CBT-E studies, whereas rates for eating pathology (56.52%) were lower. There was reliable change for eating pathology (70.83%), anxiety (69.23%), and depression (56%). However, the attrition rate means that completer analyses were likely to be over-optimistic about recovery rates (relative to ITT analyses). Future developments should focus on enhancing retention for such patients. Results suggest that CBT-AN-20 may be a viable alternative treatment to CBT-E for some adult outpatients with anorexia nervosa. A fully powered study is needed to validate CBT-AN-20's effectiveness and to explore when change occurs, for whom, and its predictors.