The lifetime prevalence of Anorexia Nervosa among females is approximately 0.5%. Individuals who are subthreshold for the disorder (i.e., with Eating Disorder Not Otherwise Specified) are more commonly encountered. The prevalence of Anorexia Nervosa among males is approximately one-tenth that among females. The incidence of Anorexia Nervosa appears to have increased in recent decades.
Specific Culture, Age, and Gender Features
Anorexia Nervosa appears to be far more prevalent in industrialized societies, in which there is an abundance of food and in which, especially for females, being considered attractive is linked to being thin. The disorder is probably most common in the United States, Canada, Europe, Australia, Japan, New Zealand, and South Africa, but little systematic work has examined prevalence in other cultures. Immigrants from cultures in which the disorder is rare who emigrate to cultures in which the disorder is more prevalent may develop Anorexia Nervosa as thin-body ideals are assimilated. Cultural factors may also influence the manifestations of the disorder. For example, in some cultures, disturbed perception of the body or fear of weight gain may not be prominent and the expressed motivation for food restriction may have a different content, such as epigastric discomfort or distaste for food.
Anorexia Nervosa rarely begins before puberty, but there are suggestions that the severity of associated mental disturbances may be greater among prepubertal individuals who develop the illness. However, data also suggest that when the illness begins during early adolescence (between ages 13 and 18 years), it may be associated with a better prognosis. More than 90% of cases of Anorexia Nervosa occur in females.
Course
Anorexia Nervosa typically begins in mid- to late adolescence (age 14-18 years). The onset of this disorder rarely occurs in females over age 40 years. The onset of illness may be associated with a stressful life event. The course and outcome of Anorexia Nervosa are highly variable. Some individuals with Anorexia Nervosa recover fully after a single episode, some exhibit a fluctuating pattern of weight gain followed by relapse, and others experience a chronically deteriorating course of the illness over many years. With time, particularly within the first 5 years of onset, a significant fraction of individuals with the Restricting Type of Anorexia Nervosa develop binge eating, indicating a change to the Binge Eating/Purging subtype. A sustained shift in clinical presentation (e.g., weight gain plus the presence of binge eating and purging) may eventually warrant a change in diagnosis to Bulimia Nervosa.
Hospitalization may be required to restore weight and to address fluid and electrolyte imbalances. Of individuals admitted to university hospitals, the long-term mortality from Anorexia Nervosa is over 10%. Death most commonly results from starvation, suicide, or electrolyte imbalance.
Familial Pattern
There is an increased risk of Anorexia Nervosa among first-degree biological relatives of individuals with the disorder. An increased risk of Mood Disorders has also been found among first-degree biological relatives of individuals with Anorexia Nervosa, particularly relatives of individuals with the Binge-Eating/Purging Type. Studies of Anorexia Nervosa in twins have found concordance rates for monozygotic twins to be significantly higher than those for dizygotic twins.