Cognitive-behavioural therapy (CBT) is commonly described as the evidence-based treatment for bulimia nervosa. But do the findings from nearly perfectly crafted trials, with stringently followed protocols and “ideal” participants apply to the “real world”? How generalizable are the findings from carefully selected participants to clinical populations where, for one, the prevalence of psychiatric comorbidities is relatively high?
In other words, CBT has been shown to be efficacious (i.e., it works in a controlled experimental research trial setting) but is it effective (i.e., does it work in a clinical setting where clients might have multiple diagnoses and complex needs)?
This is precisely the question that Glenn Waller and colleagues sought to answer. They wanted to see whether CBT would work in a “routine clinical setting, where none of the exclusion-and protocol-based constraints […] apply.”
PARTICIPANTS
Participants were recruited from a publicly-funded outpatient ED service in the UK. The only exclusion criteria were psychosis, learning difficulties, and inability to communicate in English.
78 adult women (average age: 28; average BMI: 22) entered treatment:
- 55 with bulimia nervosa (52 purging subtype and 3 with nonpurging subtype)
- 23 with EDNOS involving bulimic behaviours (9 with subthreshold BN, 10 with BED and 4 with purging but no bingeing)
- Psychiatric comorbidities were as follows:
- Major depressive disorder: 44%
- Obsessive-compulsive disorder: 26%
- Anxiety disorders: 32%
- Substance misuse: 23%
- 9 were on SSRIs, some were seeing a dietician, none were receiving other forms of therapy alongside CBT
TREATMENT
Since the purpose of the study was to see how effective CBT is in a clinical setting, the treatment protocols (such as the total number of sessions) were not set in stone. The number of sessions could be reduced or increased as deemed necessary. Overall, experienced clinical psychologists delivered an average of 19.2 one-hour CBT sessions (range: 7-80!).
Before we proceed to the findings, we should make a note first of what did the researchers defined as “remission”:
Patients were regarded as in remission if they no longer had a diagnosis of any eating disorder by the end of treatment (including being free of bulimic behaviors for at least a month prior to the last session, and not having pathological concerns about eating, weight, and shape).
SUMMARY OF MAIN FINDINGS
Dropout
Out of the 78 participants, only 8 dropped prior to completing their treatment. Interestingly, the authors could not identify any predictors of treatment dropout.
Bingeing and purging following CBT
From the 70 that completed treatment:
- 66 engaged in bingeing at the beginning of treatment; 28 at end of treatment = 58% were abstinent (meaning for at least 4 weeks prior to end, as defined by the remission criteria)
- 51 engaged in vomiting at the beginning of treatment; 26 at the end = 51% abstinent
- 17 engage in laxative abuse at the beginning of treatment; 3 at the end = 86% were abstinent
- 56% were free of bingeing and purging by the end of treatment
How many individuals were “diagnosable” following CBT?
Overall, 52.9% of the individuals that completed treatment were free of a diagnosable eating disorder by the end of treatment. If we include the 8 that dropped out and assume that they still had a diagnosable eating disorder (a reasonable and conservative assumption), then 47.4% of the 78 that started CBT could be considered in remission.
Changes in the frequency of symptoms following CBT
In terms of bulimic behaviours, the frequency of objective bingeing decreased by 59% and the frequency of vomiting dropped by 72% among those that complete (the numbers are 64% and 65% for the intent-to-treat* analysis, respectively.)
(The intent-to-treat analysis entailed “carrying forward the most recent data to substitute for missing data where a patient dropped out.” So if a patient dropped out at week 5, for example, the data for frequency of bulimic behaviours, BMI, and on the Eating Disorder Inventory and Beck Depression Scale were substituted for and used as end-of-treatment values.)
Here is a more detailed table for number nerds:
WHAT DO THESE RESULTS MEAN?
Well, the good news is that these findings are similar to what has been reported in controlled clinical experiments (see here). Yay! Well, okay, according to Waller and colleagues anyway, though I briefly skimmed the cited studies and that does seem to be the case. (But of course, authors cite studies that support their findings and omit those that do not, and I have not done a thorough search of all CBT studies in bulimia nervosa patients.)
The findings in this study should be good news for clinicians. Particularly for those who may otherwise disregard CBT because they feel the findings from clinical studies are not relevant for their patients (for example, because the findings are based on patients with no/very few psychiatric comorbidities).
The findings were broadly comparable to those found in research trials—the drop-out rate was low (10.3%), the remission rate was 50%, and there were substantial reductions in levels of pathological eating attitudes and depression. In short, these findings demonstrate that this form of CBT for bulimia nervosa is effective in treating the eating disorders in “real-life” clinical settings.
That said, there are some VERY important things to keep in mind when interpreting the findings from this study:
- There was no control group! So we don’t know what the data would be for say, a waitlist control, or a group doing interpersonal therapy. This is a big problem, in my opinion. But then, my background is mostly in C. elegans molecular genetics, where not having multiple controls makes your results unpublishable.
- Clinicians in this study were well trained and had a lot of experience working with eating disorder patients (so, results may not be so stellar for less experienced clinicians)
- Beyond regular supervision, there were no “validation checks” to make sure that clinicians were actually delivering CBT
Before I conclude, I do want to point out something that I found interesting:
Diagnostic group at the outset of treatment was not broadly predictive of change in diagnosis. However, those with purging disorder showed a mixture of positive and negative outcomes, suggesting that this form of CBT is more suitable for those who binge-eat.
I have previously suspected this to be the case, but never had the chance to actually look into the data to confirm my suspicions. Maybe this is my personal bias coming through, but I do feel like this hints as to why CBT may not be the best choice (to say the least) for anorexia nervosa, particularly restricting-type anorexia nervosa.
Anyway, what do you think? If you are a sufferer and have done CBT, has it been useful for you? If you are a clinician, what do you think of CBT? Do you utilize it in your practice?
References
Waller G, Gray E, Hinrichsen H, Mountford V, Lawson R, & Patient E (2013). Cognitive-behavioral therapy for bulimia nervosa and atypical bulimic nervosa: Effectiveness in clinical settings. International Journal of Eating Disorders PMID: 23996224
