Although it is less common than bulimia and binge eating, anorexia is perhaps the most famous eating disorder. It is often associated with teenage girls, and there is some truth in this; girls in their teens make up about 85% of anorexia diagnoses. However, anorexia affects people across all demographics.
What causes anorexia has been the subject of much debate over the last three years. Traditionally it has been regarded as a disorder with social and cultural explanations, often thought to result from a drive for thinness and physical perfection in western cultures. Others placed emphasis on gender dynamics, arguing anorexia is caused by power struggles between the sexes. But while both of these factors play a role, recent advances in science have shown that it is biology and genetics that complete the puzzle. It is through understanding the complex interaction between biology and environment that anorexia can be understood and effectively treated.
People who develop anorexia often, though by no means always, share a number of personality traits both prior to and after developing the illness. These include:
- Childhood perfectionism
- High harm avoidance
- Reduced flexibility
- Good behaviour
Research suggests that these personality traits may be directly linked to the underlying genetics of the individual, and the race is on to find specific genes that relate to the neurochemistry of eating behaviour.
One of the key biological findings is the role of a neurochemical called serotonin. Brain imaging has shown how people with anorexia normally have unusually high levels serotonin both before developing the illness and after recovering from it. Serotonin is most widely known as a ‘feel good’ chemical, as low levels of it can cause depression. However, high levels of serotonin can cause anxiety, behavioural inhibition and body perception issues. Serotonin production is directly related to food, as the body synthesises the chemical from an amino acid called tryptophan, which we get from food. If you eat less food, you get less tryptophan, and hence less serotonin. As such, for those predisposed to anorexia, not eating may reduce the symptoms of anxiety and behavioural inhibition that come with increased serotonin levels.
The problem is that the brain responds to this by increasing the amount of serotonin receptors, in order to increase sensitivity to serotonin in compensation for the lowered levels of the chemical. Then, when the person eats again, the brain floods with serotonin and old feelings of anxiety return, this time amplified. In reaction, the person returns to starving themselves in order to feel better and, in this way, starts to become locked in the anorexia trap.
Serotonin is just one of a number of chemicals involved in anorexia, and scientists are continuing their work trying to understand the roles of different areas of the brain in the disorder. Almost all are finding similar things; that the regions of the brain impacted by starvation include those that play a crucial role in emotions, personality and rewards. Many believe that anorexia shares similarities with addiction as, like drugs, self-starvation produces chemical changes in the brains which impact behaviour and emotions. This knowledge is crucial in informing ways of treating the illness.