Sleep Quality and Biomarkers in Adolescent Girls With Anorexia Nervosa

The purpose of this observational study is to systematically evaluate how a 12-month multimodal psychiatric treatment program affects sleep quality, inflammatory and hormonal biomarkers, eating disorder psychopathology, and health-related quality of life in adolescent girls (aged 10-18 years) diagnosed with anorexia nervosa. The main questions it aims to answer are: * Do adolescent girls with anorexia nervosa have measurable changes in sleep patterns (total sleep time, sleep efficiency, REM sleep, deep sleep) compared to age- and sex-matched published values, and do these improve after 12 months of psychiatric treatment? * Are specific body markers (like NLR, CRP, vitamin D, and lipid profile) linked to how severe sleep problems, eating disorder symptoms, and treatment results are in this group? * To assess these outcomes, researchers will compare participants' baseline measurements to their own 12-month follow-up measurements to determine whether multimodal psychiatric treatment produces clinically meaningful improvements in sleep architecture, biomarker profiles, psychopathology, psychological flexibility, and quality of life. Participants will: * Take-home sleep recordings with a wireless device (NOX A1) in their usual environment at the start and after 12 months of treatment. * Complete validated self-report questionnaires assessing sleep quality (PSQI), daytime sleepiness (ESS-CHAD for children and adolescents), eating disorder symptoms (EDE-Q), depression, anxiety, and stress (DASS-21), psychological flexibility (AFQ-Y8), and health-related quality of life (KIDSCREEN-52) at baseline and 12-month follow-up. * Give blood samples at the start and after 12 months for testing of inflammation markers, hormone levels, lipids, and anthropometric measurements. * Take part in a Day Hospital Program at the Department of Psychiatry, University Hospital of Split (KBC Split), Croatia, which includes Acceptance and Commitment Therapy, Cognitive Behavioral Therapy, indivi