There is no single cause for anorexia. Most experts have argued that the condition is caused by a combination of psychological, environmental and biological factors, which lead to a destructive cycle of behaviour.
A widely accepted model based on these factors is that some people have distinct personality traits that make them more vulnerable to anorexia.
Environmental factors, such as going through puberty or living in a culture where thinness is an ideal, then causes the person to begin a pattern of long-term dieting and weight loss.
The lack of a normal diet has a biological effect on the brain, which helps reinforce the obsessive thinking and behaviour associated with anorexia.
A cycle then begins. The more the person diets, the greater its effect on the brain and the greater the desire to lose weight. This means that symptoms gradually, and then rapidly, get worse.
Each of these factors is explained in more detail below.
Psychological factors
Research has found that most people who develop anorexia share certain psychological factors that help to define their personality and, to some extent, their behaviour. These include:
- a tendency towards depression and anxiety
- poor reaction to stress
- excessive worrying and feeling scared or doubtful about the future
- perfectionism – setting strict, demanding goals or standards
- inhibition – where a person restrains or controls their behaviour and expression
- feelings of obsession and compulsion (though not necessary ‘full-blown’ obsessive compulsive disorder) – an obsession is an unwanted thought, image or urge that repeatedly enters a person’s mind. A compulsion is a repetitive behaviour or mental act that a person feels compelled to perform.
Environmental factors
The fact that most cases of anorexia develop during puberty suggests that puberty itself is an important environmental factor contributing to anorexia.
It may be that the combination of the hormonal changes during puberty and feelings of stress, anxiety and low self-esteem that many teenagers have during puberty could trigger anorexia.
Another important environmental factor is Western culture and society. Girls (and, to a lesser extent, boys) are exposed to a wide range of different media which constantly reinforce the message that being thin is the only way to be beautiful, and that thinness should be pursued at all costs.
At the same time, magazines and newspapers focus on celebrities' minor physical imperfections, such as gaining a few pounds or having cellulite.
Other environmental factors that may contribute towards anorexia include:
- a stressful life event, such as losing a job or a relationship
- bereavement
- pressures and stress at school, such as exams or bullying
- difficult family relationships
- physical or sexual abuse
Biological factors
Your brain requires a healthy, nutritious diet to function normally. It uses a fifth of all the calories you eat. So the extreme dieting associated with anorexia can disrupt the normal functions of the brain, possibly making anorexia symptoms worse.
Malnutrition can also change the balance of hormones in the body, which can disrupt the normal functioning of the brain.
There are a number of theories on how the brain may be affected by anorexia. One theory is that the changes mentioned above cause the brain to become very sensitive to the effects of an amino acid called tryptophan, found in almost all types of food.
This sensitivity may then cause feelings of anxiety in people with anorexia when they eat. At the same time, starving themselves and excessive exercise is known to lower levels of tryptophan, which may make the person feel calmer and more relaxed.
Another theory is that the system controlling a person’s sense of appetite becomes disrupted.
Appetite is controlled by a part of the brain called the hypothalamus. When your body needs more food, your hypothalamus releases chemicals, known as neurotransmitters and neuropeptides, which stimulate your appetite.
Once you have eaten enough food, your body will release a hormone called leptin, which signals to your hypothalamus that you have eaten enough food. Your hypothalamus will release a different set of chemicals that essentially reward you for eating, and make you feel satisfied.
It is thought that due to changes in the brain, the ‘appetite-reward pathway’ becomes scrambled in people with anorexia. The feeling of fullness after a meal does not produce a sense of reward, but a sense of anxiety, guilt or self-loathing. In turn, feeling hungry may help to reduce these negative feelings.
