One biological explanation suggests anorexia nervosa (AN) may have a physical cause through neurotransmitter imbalances. Disruption of serotonin levels leads to increased anxiety, which may then trigger AN. Bailer et al found high levels of serotonin in women with binge eating/purging AN, with highest levels in those with the most anxiety.
Another explanation into neurotransmitters looks at dopamine over activity. Increased dopamine in the basal ganglia alters the way people interpret rewards, so individuals with AN find it difficult to associate good feelings with things that are usually pleasurable (e.g. food).
A further biological explanation is pregnancy and birth complications. Inadequate nutrition during pregnancy among mothers with an eating disorder may act as a diathesis for the development of AN in the child. Lindberg and Hjern found a significant association between birth complications and the development of AN. Also, birth complications such as lack of oxygen may cause brain damage to the child which can impair neurodevelopment of the child.
An evolutionary explanation is the ‘adapted to flee’ famine hypothesis. Typical AN symptoms of food restriction, hyperactivity and denial of starvation reflect evolved adaption in response to local famine conditions. When individuals lose weight, adaptive mechanisms usually cause conservation of energy and an increase in desire for food. This adaption must be ‘turned off’ so that individuals increase their chances of survival by moving to a more favourable environment in terms of food resources.
A problem with the serotonin explanation is that SSRIs, which alter levels of serotonin in the brain, are ineffective when used with AN patients. However, some studies report…