PurposeInsomnia and anorexia nervosa (AN) are frequently comorbid, negatively affecting the evolution and the prognosis of AN. Within this framework, the management of sleep disorders appears as critical. The aim of this retrospective study is to assess, for the first time, the efficacy of cognitive and behavioural therapy for insomnia (CBT-I) on sleep disturbances in adolescents with AN. To do so, we investigated the impact of CBT-I on sleep disturbances and sleep-related outcomes, in BMI, AN symptoms, anxiety and depressive symptoms, emotionality and quality of life. These features were compared between two groups of patients with AN, one following CBT-I, and the other receiving the regular treatment at the psychiatric unit.MethodsData collection occurred between January and May 2022. The study included 42 adolescents in-treatment at the Eating Disorders care specialised unit at Salvator Hospital in Marseille. They were randomly assigned to the CBT-I group (N = 31) or the control group (N = 11). Several clinical elements were assessed using sleep diaries and self-report questionnaires.ResultsParticipants undergoing CBT-I showed a significant improvement in sleep latency, total wake time and sleep efficacy, as well as in physical well-being. No significant effects were found regarding AN symptoms.ConclusionThese preliminary findings provide support for CBT-I effectiveness in adolescents with AN, as shown by significant improvements in several sleep parameters, as well as in physical well-being. These promising results, underline the relevance of this topic and its potential benefits for a more appropriate treatment for adolescents with AN.Level of evidence: Level V, retrospective study.