166 Chapter 8 impulse control disorders (9)/. Studies found correlations between AN and childhood trauma and between AN and specific personality traits (like perfectionism, negative emotionality and bodily dissatisfaction (12). Despite increased knowledge of neurobiological, psychological and environmental factors that contribute to the development and maintenance of the (9, 13, 14), effective treatment options are limited, and AN takes on a chronic course in a considerable number of patients (20%) (15). Neurobiology of AN Several neurobiological factors have been investigated in AN, including neurotransmitter systems and brain network functioning (16). Changes in serotonin (5-HT) and dopamine (DA) have been most often examined. Several studies show alterations in 5-HT-metabolites, -receptor binding potential and -activity, suggesting involvement of 5-HT function in AN (17, 18). Dopamine (DA) is related to motivation and reward, and to eating and the reinforcing value of food (19). Studies on DA metabolites and receptor density in AN suggest an altered DA functioning and disturbed reward processing in AN (19-22). Bailer e.a. (2017) (23) found a positive association between DA release and anxiety in the dorsal caudate in AN patients, possibly explaining why food-related DA-release produces anxiety in AN but is considered pleasurable in healthy individuals. Brain areas involved in eating and eating disorders can be classified in circuits that are interconnected and mutually interact with each other. Although difficult to compare, functional magnetic resonance imaging (fMRI) studies in AN show consistently altered activation in emotional, reward and cognitive brain networks as well as networks implied in interoception. In Supplementary Table 1, we summarize fMRI studies in ill and recovered AN patients according to Frank e.a. (2019) and O’Hara e.a. (2015) (24, 25). In summary, the structures showing dysfunctional activation in ill and recovered AN patients are part of 1) salience and reward networks related to emotional processing and reward processing, and 2) a cortical cognitive circuit related to selective attention and planning. Together they form the cortico-striatal-limbic neurocircuit, which is implicated also in other reward related psychiatric disorders such as obsessive compulsive disorder (OCD) (26). Several models refer to a dysfunctional reward circuit in AN (e.g. the bottom-up top-down model by Kaye e.a. 2009, (27)). Frank e.a. (2019) (24) suggest that there is a conflict between the conscious motivation to restrict food in AN and a body-homeostasis driven motivation to approach food. There seems to be a reinforcing mechanism between AN behavior and anxiety. Some AN behavioral symptoms provide short time relief of anxiety and stress and are rewarding.
RkJQdWJsaXNoZXIy MjY0ODMw