Emphasis on the desirability of being thin pervades Western society, and obesity is considered unattractive, unhealthy, and undesirable. However, since only a small percentage develop anorexia nervosa, other factors must be important. Some persons are probably predisposed because of undefined psychologic, genetic, or metabolic vulnerability. Anorexia nervosa is rare in areas with a genuine food shortage. Onset usually occurs during adolescence, occasionally earlier, and less commonly in adulthood.
Many patients belong to middle or upper socioeconomic classes.
However, because most mild cases are probably undiagnosed, true prevalence and mortality rates are unknown. Symptoms and Signs Anorexia nervosa may be mild and transient or severe and long-standing. Many persons who develop the disorder are meticulous, compulsive, and intelligent, with very high standards for achievement and success. Preoccupation and anxiety about weight increase, even as emaciation develops. Denial of the disorder is a prominent feature.