I know I've written several posts about the diagnostic criteria of eating disorders. It's a hot topic of debate as the new DSM-V undergoes revisions for a variety of disorders. I came across this article from a few months ago which looked at the crossover rate in eating disorders. By crossover, this mean changing from an anorexia to bulimia diagnosis and vice versa.
This longitudinal study consisted of 216 woman with anorexia, anorexia subtypes of restricting or binge/purge, and bulimia over a period of 7 years. The average duration of illness was 6 years among the women. Based on symptomology, each were assessed weekly with a diagnosis.
The results indicated that almost three-quarters of the patients with anorexia crossed over, about half of that number switched within the anorexia subtype, almost one tihrd crossed over to bulimia, leaving a small number who did not cross over at all. Of those with a diagnosis of anorexia restricting type, a little over half crossed over into either binge/purge type anorexia or bulimia. Those with an initial diagnosis of bulimia had a much lower rate of crossing over. The small minority that experienced this changed to binge/purge type anorexia.
Besides the diagnostic changes, results also indicated that a significant number from each group had partial recovery. Those reaching full recovery was higher for the bulimia group versus the anorexia group, including subtypes. In about half of those with anorexia who crossed over to bulimia, happened while obtaining partial or full recovery. This could indicate that it isn't really a change in disorder so much as a stage in illness. The other half of anorexics who crossed over to bulimia crossed back to anorexia which could indicate that those with a lifetime history of anorexia are more prone to relapse into anorexia.
Essentially, this study shows the frequency of cross over between anorexia, its subtype, and bulimia. This questions the validity of having anorexia subtypes in the first place. It seems that it is not likely a change of disorders, but rather a more apparent of stage of illness. I should note that this study did not look at non-purging bulimics nor EDNOS as it was not recognized in the DSM at that time.
I thought this was an interesting study overall. The fact that it was longitudinal was very helpful in showing how so many individuals flip flop back and forth between anorexia and bulimia. It was also sobering that many reached partial recovery and a good number full recovery. In general, this study implicates further the need for better diagnostics for eating disorders. I hope the DSM-V will provide that.
If you go to the full text, you can download it for free. The graphs shown give a better idea of the frequency of cross over and recovery rates.