Anorexia nervosa is a characterised disorder which forms part of the wider spectrum of eating disorders. It is a common pathology, particularly in adolescence, with a complex, severe prognosis in both somatic and psychiatric terms, and significant psychosocial consequences, particularly for family relationships. The treatment of anorexia requires a multidisciplinary team of specialists who can offer individual and family-based approaches. International recommendations highlight the encouraging results of family therapy in the treatment of anorexia nervosa in adolescence. Various types of family approach exist, including Family Based Treatments, which are a specific but highly effective approach, particularly widespread in the United States. Multifamily therapy (MFT), which involves bringing several families together to address the problem of anorexia, has proved effective for several years now. Since January 2019, multifamily therapy has been offered to adolescents aged 12 to 18 who are being followed at the Maison de Solenn-Maison des Adolescents at Cochin hospital, for anorexia nervosa, as well as their families. Each group brings together 5 to 7 families and comprises 10 3-hour sessions, with 3 weeks between each session. 2 groups are offered per year. Multi-family therapy therefore involves 10 to 14 families per year. It complements the other approaches available in the department. To be able to describe the therapeutic processes at work in multifamily groups in order to be able to better describe our therapeutic device and envisage possible modifications. These processes would be broken down into four areas: MFT and its effects on the anorexic symptom, MFT and its effects on the family, MFT as group therapy and ways of improving the MFT system.