Predictors of Adolescent Eating Disorders
ABSTRACT & COMMENTARY
Synopsis: A history of dieting is an important predictor of new eating disorders. Differences between the incidence of eating disorders between the sexes are largely accounted for by the high rates of earlier dieting and psychiatric morbidity in adolescent girls.
Source: Patton GC, et al. Onset of adolescent eating disorders: Population based cohort study over 3 years. BMJ 1999;318:765-768.
Patton and associates from the university of melbourne in Australia designed a large prospective, population-based cohort study that followed more than 1500 students initially aged 14-15 years from 44 secondary schools in the State of Victoria, Australia, in an attempt to identify predictors of a new eating disorder in a cohort of adolescent children who were followed for three years. The outcome measures used included weight and height, a history of dieting (determined by an adolescent dieting scale), psychiatric morbidity (determined by a clinical interview schedule), and eating disorder (defined by a branched eating disorders test). Eating disorder was defined when a subject met two criteria for anorexia nervosa or bulimia nervosa according to the Diagnostic and Statistical Manual, fourth edition (DSM-IV). At the beginning of the study, 3.3% (29/888) of the female subjects had partial syndromes of eating disorders as defined above. Only 0.3% (2/811) of males had partial syndromes of eating disorders. The rate of development of new eating disorders per 1000 person-years of observation was 21.8 in females and 6.0 in males. Female subjects who 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 moderate level were five times more likely to develop an eating disorder than those who did not diet. Psychiatric morbidity predicted the onset of an eating disorder independently of dieting status so that those subjects in the highest morbidity category had an almost sevenfold increased risk of developing an eating disorder. After adjustment for earlier dieting and psychiatric morbidity, body index, extent of exercise, and sex were not predictive of new eating disorders. Patton et al conclude that dieting is the most important predictor of a new eating disorder in adolescent children. Differences in the incidence of eating disorders between sexes were largely accounted for by the high rates of earlier dieting and psychiatric morbidity in females. In the adolescent, controlling weight by exercise rather than diet restriction seems to carry less risk of development of an eating disorder.
Comment by Walter R. Anyan, Jr., MD, FAAP
Patton et al designed a large prospective, population-based cohort study which, over three years, evaluated 1947 students initially 14-15 years of age from 44 secondary schools in Victoria. In an attempt to identify predictors of a new eating disorder in these adolescents, they measured height and weight, obtained a history of dieting (determined by an adolescent dieting scale), evaluated psychiatric morbidity (determined by a clinical interview schedule), and presence of an eating disorder (defined by a branched eating disorders test). Partial eating disorder was defined when a subject met two criteria for anorexia nervosa or bulimia nervosa, according to the DSM-IV.
At the beginning of the study, 3.3% of the female subjects and 0.3% of the male subjects had partial syndromes of eating disorders. The subsequent rate of development of new eating disorders per 1000 person-years of observation was 21.8 times more likely, and those who dieted at a moderate level were five times more likely to develop an eating disorder within six months than those who did not diet. Psychiatric morbidity also predicted the onset of an eating disorder independently of dieting status, and those subjects in the highest morbidity category had an almost sevenfold increased risk of developing an eating disorder. Patton et al conclude that dieting is the most important predictor of a new eating disorder in adolescents. Differences in the incidence of eating disorders between the sexes were largely accounted for by the high rates of earlier dieting and psychiatric morbidity in females. In the adolescent, controlling weight by exercise rather than diet restriction seems to carry less risk of development of an eating disorder.
There are three wrinkles in this study. 1) It is important to note that the full syndrome of bulimia nervosa was found in only two girls and the full syndrome of anorexia nervosa was not found in anyone. 2) There is some discordance between the finding that the incidence of new eating disorders was 3.5 times greater in females and the observation that 8% of females vs. 0.5% of males dieted at severe levels. It would seem that, in terms of subsequent development of an eating disorder, severe dieting might be a more significant act when found in a male. 3) The DSM-IV diagnostic criteria for eating disorders were not created as equals: two criteria for anorexia nervosa are objective and two are subjective; two criteria for bulimia nervosa are behavioral, one is subjective; and the other is simply the absence of anorexia nervosa. Consequently, some combinations of criteria might be more ominous than others.
However, the results fit clinical experience, as one of the most characteristic events in the history of a patient with anorexia nervosa is the decision to lose weight or reshape one’s body. Often, the decision involves a weight goal that seems reasonable, but once it is achieved through the use of an increasingly stringent diet and exercise, it is replaced by the pursuit of thinness and the disorder becomes full-blown. In contrast, adolescents who develop bulimia nervosa attempt to resolve their dissatisfaction with body size and shape by inducing vomiting, imposing severe diets, and taking laxatives and other medications. While some lose weight, most shuttle back and forth over a range of 7-10 pounds.
This study suggests that it’s worthwhile to ask adolescents—and probably younger kids as well—whether they’ve been dieting, even though some will assume that you think they’ve lost weight, and others will think that you are hinting that they should! A positive answer, however, can generate a careful assessment of the situation and a good discussion of whether weight loss makes any sense. (Dr. Anyan is Professor of Pediatrics and Chief of the Division of Adolescent Medicine at Yale University School of Medicine.)
The most important predictor of a new eating disorder in adolescent children is:
a. depression.
b. extent of exercise.
c. dieting.
d. None of the above
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