- characterized by aberrant patterns of eating behaviour and weight regulation which result in weight loss and endocrine abnormalities such as amenorrhea, disturbances in attitude and perception about weight and shape, and an intense fear of gaining weight. This thesis is based upon a follow up cohort study of 61 young girls and women consecutively referred to two specialized eating disorder treatment centres, one for adolescents (at the Dept. of Child and Adolescent Psychiatry of the University Medical Centre Utrecht) and one for adults (Rintveld, centre for Eating Disorders, Altrecht Mental Health Institute). The study focused on psychoneuroendocrinological changes during treatment; changes in body weight and composition, in hormones, activity level and mood states. After a follow-up of maximum one year, the patients were divided into 3 groups according to their clinical status: no weight recovery and ongoing amenorrhea (NWR, nineteen patients), weight recovery but with ongoing amenorrhea (WR, eighteen patients), and weight and cycle recovery (WCR, twenty-four patients). Approximately 5 years after the first admission a follow up was conducted to investigate the current state of illness as well as to identify potential predictors of recovery. All hormones changed over time with weight gain, with ACTH being the only exception to this rule. If normal values were reached this occurred in the WCR group only. Several factors predicted and influenced complete physical recovery in the first year. A novel finding is that the ovarian markers AMH, Inhibin B together with FSH predict which participants will regain a regular menstrual cycle with weight gain. Leptin levels did predict physical recovery, we detected a threshold level; an initial leptin level 2 microgr./L increased chances for a full recovery to 75%. We replicated the finding by Holtkamp et al. (2006) that hyperactivity is related to leptin in the acute stage of AN but only when we compared an age matched group, the youngest patients in this study. Activity levels however are not predictive for treatment outcome in the first year in our study sample. Interestingly, chances for a patient that shows recovery in the first year, to relapse at 5 years are correlated with leptin and activity level at T1, a novel finding. Without physical recovery there is no psychological recovery, but the factors that influence psychological recovery need further study. Although at 5 years FU 59% of the participants had become physically recovered and 52% did not meet criteria for an eating disorder, many still spent a lot of time and energy on thoughts concerning food or their body. Most striking are the data on the anxiety and depressive symptoms that are in line with the findings of Herpertz-Dahlmann and colleagues (2001).