When I was a medical student, I remember doing a psych rotation on a pediatric ward.  I was struck by how many of the admissions were for eating disorders and even before then, I was aware that more than a small number of my female friends and acquaintances were suffering from some form of disordered eating, so when I saw a paper on that topic, I was more than a little intrigued.  This is Healthcare Triage News.

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To the research!  "The effects of sorority membership on eating disorders, body weight, and disordered eating behaviors."  This study sought to get more at the causality link between sororities and a number of outcomes including weight, disordered eating, and eating disorders using the American College Health Association survey.  It included more than 144,000 students from 123 colleges and three semesters in the United States.  It contained data on their health and weight-related attitudes, perceptions, and behaviors.  It also showed whether or not they were in a sorority.  

It's not perfect.  Some data on family background are limited, but it has information on some socioeconomic factors as well as racial ones and ones on many other health behaviors.  Moreover, the researchers used propensity score matching and instrument variables, which are sophisticated techniques to try and get towards causality without using a randomized controlled trial.  

Propensity score use involves matching those in an intervention group, like sorority membership, with at least one subject in the control group, non-members, who are as similar as possible on the many measurable characteristics in the data set.  This allows you to be sure that differences are because of the variable of interest. 

The instrument variable chosen for this analysis was the percent of males at the same college joining a fraternity.  This was assumed to be predictive of sorority membership but have no effect on the outcomes after controlling for other factors.  Using such a variable on the analysis also helps to get closer to proving causality.  

The results?  The study found that sorority membership did have an effect on obesity (there was less of it), and BMI (which was lower in general), but it didn't have an effect on being underweight.  Membership did, though, have a significant effect on disordered eating behaviors and diagnosed eating disorders, especially with behaviors like vomiting and laxative pill misuse, but when they implemented the more sophisticated methods, they found that it wasn't as clear as you might think.  I'm gonna let the authors' discussion speak for itself.

"Namely, in both of these exercises, we find evidence that there are possibly no positive causal effects of sorority membership on our outcomes with the exception of BMI.  That is, we can only conclude that sorority membership leads to lower BMI for those females joining a sorority, but we cannot exclude the possibility that sorority membership has no effect on sorority members' other weight outcomes, disordered eating behaviors, and eating disorders.  These results, casting doubts on the common belief that sororities are a main cause for adverse weight-related outcomes for college women, have the important policy implications that programs targeted at reducing the prevalence of these adverse outcomes might not reach their goal if they focus on sororities.  Limited resources need to be allocated elsewhere."  

These results were interesting and surprising to me.  It's something to think about.  I look forward to seeing what others think of this study.

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