Participants

Study data were obtained from 54 underweight female patients with acute AN diagnosed according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-5; American Psychiatric Association, 2013; age range 12–24 years). Two acAN were excluded after quality control of the structural MRI (sMRI) data (see online Supplementary Information 1.4.2), resulting in a final sample of 52 acAN. The additional HC group consisted of 149 female participants (age range 12–23 years) of whom two were excluded after quality control (final sample of 147 HC participants). The sample partially overlaps with our previous studies (Bahnsen et al., 2022; Bernardoni et al., 2016; Hellerhoff et al., 2021; see online Supplementary Information 1.1 for Details). AN patients were studied in the acutely underweight state (acAN-TP1) not more than 96 h after admission to intensive treatment and reassessed after short-term partial weight restoration (acAN-TP2; after an a priori-defined minimum BMI increase of 10%; all patients in the present sample had a BMI increase >14%). Participants with AN underwent treatment in eating disorder programs at a tertiary care university hospital. 98% of the participants identified as European (details in online Supplementary Information 1.1). The authors assert that all procedures contributing to this work comply with the ethical standards of the relevant national and institutional committees on human experimentation and with the Helsinki Declaration of 1975, as revised in 2008. All participants (and the legal guardians of underage participants) gave written informed consent.

AN was diagnosed using a modified version of the German expert form of the Structured Interview for Anorexia and Bulimia Nervosa (SIAB-EX; Fichter & Quadflieg, 1999) and required a BMI < 17.5 kg/m² (or below the 10th age percentile, if younger than 15.5 years). HC had to be of normal weight, eumenorrhoeic, and without any history of psychiatric illness. Several additional exclusion criteria were applied to both AN and HC participants, including psychotropic medication in the four weeks preceding study participation (except for selective serotonin reuptake inhibitors, which were allowed in AN participants, n = 1 in acAN-TP1 and n = 2 in acAN-TP2; online Supplementary Information 1.1).