Eating disorders are a common problem among adolescent girls; as many as 5.7 percent have been diagnosed with anorexia, bulimia, binge eating, or other such conditions. Despite their prevalence, however, eating disorders often go unrecognized, and most people who suffer from one do not know it.

To be able to effectively identify and treat eating disorders, we must be aware of their signs and risks. These range from biological factors such as brain size and sexual orientation to environmental factors like mother-daughter relationships and the number of hours spent watching TV. Now, new research has shown that the school a girl attends can affect her risk of developing an eating disorder, too.

Published in the International Journal of Epidemiology, the study was carried out by researchers in the United Kingdom and Sweden. The team evaluated routinely collected Swedish data in order to see if there were patterns in the rate of eating disorder diagnoses at different schools.

Before comparing the data from different schools, the researchers controlled for factors that would make certain groups of girls more likely to develop eating disorders, such as parental income, family mental health history, number of siblings, and birth weight. Even after accounting for these factors, the researchers still observed noticeable differences in the rates of eating disorders at certain schools.

“For a long time, clinicians in the field have noted that they seem to see more young people with eating disorders from some schools than others, but this is the first empirical evidence that this is the case,” said Dr. Helen Bould, head of the research team and a child and adolescent psychiatrist at England’s University of Oxford, in a press release.

The data revealed that girls who attended schools with a higher percentage of female students and college-educated parents were more likely to be diagnosed with an eating disorder than those at schools with fewer female students and college-educated parents.

“Unfortunately, this study can't tell us what it is about schools that affects the rates of eating disorders: It might be an unintentional effect of the aspirational culture of some schools that makes eating disorders more likely; it might be that eating disorders are contagious and can spread within a school. On the other hand, it could be that some schools are better than others at identifying eating disorders in their students and ensuring they get diagnosed and treated,” Bould said.

Sweden, unlike the UK and United States, does not have any single-sex schools. In these schools, which are highly selective and likely have a high proportion of college-educated parents, the rates of eating disorders could be even higher, the researchers suspect.

Eating disorders are extremely prevalent among young girls, and they are especially dangerous to them. For example, someone with bulimia is about twice as likely to die young as someone without it. Young people with anorexia are six times more likely to die.

“Eating disorders have an enormous effect on the lives of young people who suffer from them — it is important to understand the risk factors so that we can address them,” Bould said.

Source: Bould H, et al. The influence of school on whether girls develop eating disorders. International Journal of Epidemiology. 2016.