Sleep and blood tests could unlock anorexia recovery clues in teens

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: 1. Female sex assigned at birth 2. Age between 10 and 18 years (inclusive) at the time of study enrollment 3. First-time diagnosis of anorexia nervosa according to ICD-10 criteria at the time of enrollment, including: * Anorexia nervosa (F50.0) * Atypical anorexia nervosa (F50.1) * Eating disorder, unspecified (F50.9) with predominant restrictive or anorexic presentation 4. Currently under the care of a child and adolescent psychiatrist at the Department of Psychiatry, University Hospital of Split (KBC Split), Croatia 5. Enrolled in or eligible for the Day Hospital Program for Children and Adolescents at the Department of Psychiatry, KBC Split 6. Ability to read and understand Croatian language sufficiently to complete self-report questionnaires 7. Parent or legal guardian willing and able to provide written informed consent prior to any study procedure 8. Participant willing and able to provide written assent prior to any study procedure 9. Participant and parent/guardian willing to undergo all study procedures at both time points, including: * Home polysomnography (NOX A1) at baseline and 12-month follow-up * Completion of all self-report questionnaires at baseline and 12-month follow-up * Fasting blood sampling at baseline and 12-month follow-up Exclusion Criteria: 1. Age younger than 10 years or older than 18 years at the time of enrollment 2. Male sex assigned at birth 3. Previous diagnosis of anorexia nervosa prior to current enrollment (i.e., recurrent or relapsing AN - this study enrolls first-diagnosis cases only) 4. Anorexia nervosa currently in clinical remission at the time of enrollment 5. Comorbid psychiatric diagnosis of any of the following: * Intellectual disability (any severity, ICD-10: F70-F79) * Autism spectrum disorder (ICD-10: F84) * Schizophrenia spectrum or other psychotic disorder (ICD-10: F20-F29) * Bipolar affective disorder, any type (ICD-10: F31) * Substance use disorder, any substance (ICD-10: F10-F19) 6. Severe or chronic somatic illness documented in medical history, including but not limited to: * Central nervous system disorders (epilepsy, acquired brain injury, neurodegenerative disease, ICD-10: G00-G99) * Chronic inflammatory or autoimmune disease (e.g., inflammatory bowel disease, systemic lupus erythematosus, rheumatoid arthritis) * Primary endocrine disorder independent of AN (e.g., primary hypothyroidism, type 1 or type 2 diabetes mellitus, congenital adrenal hyperplasia) * Active or history of malignancy * Chronic renal or hepatic disease 7. Use of any medication known to significantly alter sleep architecture or inflammatory biomarker levels that was initiated prior to study enrollment and is unrelated to the study treatment program, including: * Benzodiazepines or z-drugs (zopiclone, zolpidem) * Antipsychotic medications * Systemic corticosteroids * Immunosuppressive agents * Melatonin or melatonin receptor agonists Medications initiated as part of the Day Hospital treatment program after enrollment will be documented and included as covariates in statistical analyses and do not constitute an exclusion criterion. 8. Presence of an active somatic condition at the time of enrollment requiring acute inpatient medical treatment (e.g., severe electrolyte imbalance requiring intravenous correction, acute cardiac arrhythmia) that would preclude safe participation in the Day Hospital Program 9. Physical or cognitive inability to cooperate with home polysomnography device placement or self-report questionnaire completion, as judged by the treating child and adolescent psychiatrist 10. Simultaneous participation in another interventional clinical trial that could influence sleep parameters, nutritional status, inflammatory markers, or psychiatric outcomes. 11. Absence of written informed consent from parent or legal guardian, or absence of written assent from the participant