The Instability of Eating Disorder Diagnoses

Eating disorders are rarely static. Symptoms fluctuate, waxing and waning as circumstances change. Often, these fluctuations lead to diagnostic crossover–between subtypes of one disorder or to a different eating disorder altogether. The heterogeneity of symptom severity and frequency led to the establishment of the “eating disorder not otherwise specified” diagnosis in the Diagnostic and Statistical Manual. Essentially, it is everything that doesn’t quite fit into the “anorexia nervosa” or “bulimia nervosa” categories. (For example, I would guess that it is a common diagnosis for patients who fail to meet the “amenorrhea” criterion for the AN diagnosis.)

ED-NOS is a category for everything that doesn’t conform to some rather arbitrary criteria required for bulimia nervosa and anorexia nervosa, meaning: it is the diagnosis for a lot of people. Okay, that’s not very scientific, I know, but I wouldn’t trust these numbers anyway–usually people who fall into this category don’t feel “sick enough” to seek treatment, in the USA they have difficulty getting treatment coverage, and many just don’t think they have a problem (and nor do those around them). I know a fair number of people who fall into this category.

Maybe they haven’t lost quite enough weight, or they don’t binge and purge 2 times/week–maybe it is just once a week but the rest of the week they fast. Maybe they are eating a normal amount of calories but it is limited to a handful of foods that are “permissible” in that person’s mind. What if their body, their weight, the calories they consume rule their life–in the sense that it determines how they feel, what they do, who they interact with and how often, and so on. How about if they don’t binge but purge every normal meal they eat and yet maintain a weight above what is required for the AN diagnosis?

I think most clinicians (certainly most women and men with EDs) wouldn’t hesitate to say that individuals who fall into those categories have an eating disorder. They could be on their way to fulfilling the full diagnostic criteria of BN or AN, or they could be transitioning from one disorder to another, or this is just how their eating disorder manifests.

Right now, these hypothetical individuals would be lumped into the ED-NOS category. But there are several problems with the ED-NOS diagnosis , several of which are outlined in the box below.

• It is clearly not a useful diagnosis: diagnoses are meant to provide a meaningful description of the condition, ED-NOS doesn’t.
• Individuals with ED-NOS often feel like their disorder isn’t “real”, “severe enough”, or warrants professional help. (Nothing could be further from the truth.)
• Insurance companies often don’t cover it (perhaps because it is perceived as less severe?)
• DSM guides research (an AN group is selected based on fitting the DSM criteria, for example). But how useful or representative are these findings if most people don’t fit neatly into these groups?
• More importantly, how useful are they if they might fit into it at the time of the study’s recruitment but not 3 weeks later?

Given that the new edition of the Diagnostic and Statistical Manual is due to come out in 2013, it is necessary to evaluate the validity and utility of the current classification categories, and change accordingly.

This is precisely what Eddy et al. sought to do in their 2008 paper titled “Diagnostic Crossover n Anorexia Nervosa and Bulimia Nervosa: Implications for DSM-V”.

Individuals were grouped based on their initial diagnosis (AN-restricting type, AN-binge eating/purging type and BN) and followed weekly for the next seven years. Here is summary of what they found (click to enlarge):

The results are not surprising to me, but it is nice to see them in print.

There are some things that you might be wondering about: partial recovery and full recovery rates seem pretty high, what gives? Well the mean sample age was almost 25 years old (the AN patients were slightly younger than the BN patients, interesting to note, given that AN to BN transition was more common (this relates to my issue with the author’s conclusion).  But most importantly: the mean duration of the illness at intake was 6 years for AN and 6.7 for BN. That’s a considerable amount of time, which may explain the relatively high partial and full recovery rates–and yet at the same time, highlights just for how many people an eating disorder is a lifelong battle (not necessarily in symptoms but mentally). This is especially true when you consider that all of the participants were seeking treatment.

My own experience falls very much in-line with this study’s findings:  diagnosed with AN-R, following partial recovery, back to AN-R, partial recovery, AN-BP, AN-R, AN-BP, BN, partial recovery (a.k.a., beginning of restriction and weight loss), AN-R, AN-BP, AN-R, AN-BP, BN, partial recovery/symptom remission. Okay, that’s not exact, but pretty damn close.

I think this study brings to light the difficulty of studying eating disorders. But at the same time may explain why the field has been relatively unsuccessful in finding genes that are highly correlative to a particular disorder. That’s not something I’d expect to find give that eating disorder symptoms (and diagnoses) fluctuate over the duration of the disorder. And how useful are the studies that focus on that minority population that do not experience diagnosis crossover?

With regard to the first question, I think you are more likely to find correlations between specific personality traits than particular symptoms. That’s just my hunch. With regard to the second question, I think this is the best we can do at the moment but presumably, if we study the minority non-diagnostic crossover groups, we will be able to extrapolate into that more diagnostically heterogeneous majority.

One main shortcoming of this study: only women diagnosed with AN or BN at intake are included because the ED-NOS category was not established when the study began.  The authors also note the need to differentiate between ED-NOS and partial recovery (I fully agree!).

I have one issue with the conclusion that Eddy et al. (and others) come to:

These findings support the longitudinal distinction of anorexia nervosa and bulimia nervosa but do not support the anorexia nervosa subtyping schema.

I’m not so sure:  the average duration of the illness prior to the commencement of the study was 6-7 years.  Certainly it is conceivable (and I would argue the findings would support this) that many of the women that at the beginning of this study were diagnosed as BN, or even AN-BP, initially struggled with AN-R (perhaps even for years).

I’m quite interested in this topic and there are several good articles on how the DSM-V diagnostic criteria should change and the implications of particular changes. This group has some more recent articles published, following up on this, and I hope to cover them in future posts.

References

Eddy, K.T., Dorer, D.J., Franko, D.L., Tahilani, K., Thompson-Brenner, H., & Herzog, DB,. (2008). Diagnostic crossover in anorexia nervosa and bulimia nervosa: implications for DSM-V. American Journal of Psychiatry, 165 (2), 245-250 PMID: 18198267