Anorexia nervosa is a psychiatric diagnosis that describes an eating disorder characterized by low body weight and body image distortion with an obsessive fear of gaining weight. Individuals with anorexia often control body weight by voluntary starvation, purging, vomiting, excessive exercise, or other weight control measures, such as diet pills or diuretic drugs. It primarily affects adolescent females in the Western world. Anorexia nervosa is a complex condition, involving psychological, neurobiological, and sociological components

Anorexia is a life-threatening condition that can put a serious strain on many of the body's organs and physiological resources; it has one of the highest mortality rates of any psychiatric condition, with approximately 10% of people diagnosed with the condition eventually dying due to related factors

The distinction between the diagnoses of anorexia nervosa, bulimia nervosa and eating disorder not otherwise specified (EDNOS) is often difficult to make in practice and there is considerable overlap between patients diagnosed with these conditions. Furthermore, seemingly minor changes in a patient's overall behaviour or attitude (such as reported feeling of 'control' over any bingeing behaviour) can change a diagnosis from 'anorexia: binge-eating type' to bulimia nervosa. It is not unusual for a person with an eating disorder to 'move through' various diagnoses as his or her behavior and beliefs change over time

There has been a significant amount of work into psychological factors that suggests how biases in thinking and perception help maintain or contribute to the risk of developing anorexia

Sociocultural studies have highlighted the role of cultural factors, such as the promotion of thinness as the ideal female form in Western industrialised nations, particularly through the media. A recent epidemiological study of 989,871 Swedish residents indicated that gender, ethnicity and socio-economic status were large influences on the chance of developing anorexia, with those with non-European parents among the least likely to be diagnosed with the condition, and those in wealthy, white families being most at risk