Onset of adolescent eating disorders: population based cohort study over 3years

Objective To study the predictors of new eating disorders in an adolescent cohort. Design Cohort study over 3 years with six waves. Subjects Students, initially aged 14-15 years, from 44 secondary schools in the state of Victoria, Australia. Outcome measures Weight (kg), height (cm), dieting (adolescent dieting scal e), psychiatric morbidity (revised clinical interview schedule), and eating disorder (branched eating disorders test). Eating disorder (partial syndro me) was defined when a subject met two criteria for either anorexia nervosa or bulimia nervosa according to the Diagnostic and Statistical Manual of M ental Disorders, fourth edition (DSM-IV). Results At the start of the study, 3.3% (29/888) of female subjects and 0.3 % (2/811) of male subjects had partial syndromes of eating disorders. The r ate of development of new eating disorder per 1000 person years of observat ion was 21.8 in female subjects and 6.0 in male subjects. Female subjects w ho dieted at a severe level were 18 times more likely to develop an eating disorder than those who did not diet, and female subjects who dieted at a m oderate level were five times more likely to develop an eating disorder tha n those who did not diet. Psychiatric morbidity predicted the onset of eati ng disorder independently of dieting status so that those subjects in the h ighest morbidity category had an almost sevenfold increased risk of develop ing an eating disorder. After adjustment for earlier dieting and psychiatri c morbidity, body mass index, extent of exercise, and sex were not predicti ve of new eating disorders. Conclusions Dieting is the most important predictor of new eating disorders . Differences in the incidence of eating disorders between sexes were large ly accounted for by the high rates of earlier dieting and psychiatric morbi dity in the female subjects. In adolescents, controlling weight by exercise rather than diet restriction seems to carry less risk of development of ea ting disorders.