Anorexia Nervosa (AN) is a complex and multifactorial psychiatric disease that affects mostly women and is characterized by a self-restriction of food intake leading to life-threatening consequences whose underlying mechanisms are largely unexplored. AN encompasses a constellation of risk factors including genetic, biological, neuro-psychological and social factors. Although AN has a prevalence of only 1-3% in the general population, it has the highest mortality rate amongst any psychiatric disorder. Recovery of normal feeding behaviour in patients often requires several months with a large between-patient variability and a high percentage of relapse, which can occur in 35 to 41% of the patients. There is a huge unmet need for optimal understanding of processes underlying relapse. Reward processing abnormalities represents an important hypothesis underlying AN development and perpetuation. We aim to investigate the mechanisms that contribute to the maintenance and chronicity of the disease after inpatient treatment with a longitudinal design across intensive standardized inpatient treatment. We will challenge our hypothesis through brain imaging, neuropsychological, metabolic and genetic approaches. One hundred twenty-five AN female patients admitted for intensive inpatient treatment will be recruited and evaluated: at admission, after weight recovery and at 6 months after discharge with neurocognitive tests (including the Delay Discounting Task), genetic/epigenetic examination, hormonal blood samples (at each visit and repeated sampling around a meal for a 10-patient subgroup) and brain imaging (including fMRI during a Delay Discounting Task for fifty patients). One hundred healthy controls will be also recruited and be subjected to the same study procedures.