An eating disorder is a mental disorder defined by abnormal eating habits that negatively affect a person's physical and/or mental health. They include binge eating disorder, where people eat a large amount in a short period of time; anorexia nervosa, where people eat very little due to a fear of gaining weight and thus have a low body weight; bulimia nervosa, where people eat a lot and then try to rid themselves of the food; pica, where people eat non-food items; rumination syndrome, where people regurgitate food; avoidant/restrictive food intake disorder (ARFID), where people have a reduced or selective food intake due to some psychological reasons (see below); and a group of other specified feeding or eating disorders. Anxiety disorders, depression and substance abuse are common among people with eating disorders. These disorders do not include obesity.The causes of eating disorders are not clear, although both biological and environmental factors appear to play a role. Eating disorders affect about 12 percent of dancers. Cultural idealization of thinness is believed to contribute to some eating disorders. Individuals who have experienced sexual abuse are also more likely to develop eating disorders. Some disorders such as pica and rumination disorder occur more often in people with intellectual disabilities. Only one eating disorder can be diagnosed at a given time.Treatment can be effective for many eating disorders. Treatment varies by disorder and may involve counselling, dietary advice, reducing excessive exercise and the reduction of efforts to eliminate food. Medications may be used to help with some of the associated symptoms. Hospitalization may be needed in more serious cases. About 70% of people with anorexia and 50% of people with bulimia recover within five years. Recovery from binge eating disorder is less clear and estimated at 20% to 60%. Both anorexia and bulimia increase the risk of death.In the developed world, anorexia affects about 0.4% and bulimia affects about 1.3% of young women in a given year. Binge eating disorder affects about 1.6% of women and 0.8% of men in a given year. Among women about 4% have anorexia, 2% have bulimia, and 2% have binge eating disorder at some time in their life. Rates of eating disorders appear to be lower in less developed countries. Anorexia and bulimia occur nearly ten times more often in females than males. Eating disorders typically begin in late childhood or early adulthood. Rates of other eating disorders are not clear.