Why do some people recover anorexia nervosa relatively quickly while others seem to struggle for years or decades? Does it depend on the person’s desire to get better? Their willpower? How much they are willing to fight? Is it just that some try harder than others? Some might say yes, but most will correctly realize that the picture is much, much more complex.
We can spend hours talking about barriers to treatment, but in this post I want to talk about something slightly different, something perhaps that is perhaps less “obvious.”
Suppose a group of girls–all roughly the same age, same illness duration, same socioeconomic background and race–enter the same treatment facility. What determines why some will do well in treatment and continue to do well after discharge, whereas others will relapse immediately after discharge, and yet others won’t respond to treatment at all? We know that catching eating disorders early is crucial, but what else is important?
There will never be a treatment that will work for all eating disorder patients. But some types of treatment will work better than others for particular populations of ED patients. Identifying what treatment approaches work best for what subgroups is crucial if we want to improve recovery rates. In order to do that, we also need to identify what factors are associated with recovery and what factors are associated with increased illness duration, so that we can develop approaches to target specific patients groups.
Identifying prognostic factors associated with illness duration and recovery could have crucial benefits. First, it would help patients, family members, and treatment providers manage expectations for illness duration and plan treatment options. Second, it would potentially assist providers in identifying which patients are at highest risk for developing a lengthy course or chronic illness. Third, it would aid providers in tailoring treatment to target each patient’s individual risk factors for a longer length of illness while also reinforcing the patient’s unique protective factors for recovery. Increasing the intensity or specificity of early treatment for the most at-risk patients could, in turn, shorten illness length or prevent chronicity.
In this study, Stephanie Zerwas and colleagues (2013) identified prognostic factors associated with recovery from anorexia nervosa using a retrospective study design. To be included in the study, women had to have been diagnosed with AN (excluding the amenorrhea criterion), be between 13-65, have had AN at least three years prior to study (this is to reduce likelihood that participants will develop binge eating in the future, because it usually develops within first three years), and have had AN onset before the age of 25.
In total, they had 680 AN women from nine different sites across North America and Europe, fill out questionnaires and complete structured interviews on eating disorder history, behaviours, personality and temperament, and comorbid disorders.
In this study, recovery was defined as 12 months symptom free. Of the participants, only 18.1% met this criteria (but they have been recovered for an average of 5.7 years). The mean age of the participants was 26. Below is a more comprehensive summary of the sample demographics as well as the personality traits and comorbid diagnoses:
(Unfortunately, I couldn’t easily find the values for the personality questionnaires for normal healthy controls online, so it is hard for me to get a sense of how these data compare to healthy controls. If anyone has links, please let me know.)
I’m not going to bore you with the statistical models, but long story short, a few predictors of recovery emerged. In the table below, I summarized the factors that reached significance. A hazard ratio of greater than one indicates that the factor is associated with a higher likelihood of recovery whereas a hazard ratio of less than one indicates a lower probability of recovery. (Click here to find out about confidence intervals.)
So what did Zerwas and colleagues find? First, vomiting was strongly associated with a lower likelihood of recovery. Trait anxiety was also associated with a lower likelihood of recovery.
Interestingly, impulsivity was associated with a higher likelihood of recovery, though the relationship between impulsivity and recovery varied through time. Of note, a diagnosis of avoidant personality disorder also decreased the likelihood of recovery but did not reach significance in the final model.
WHAT DOES THIS MEAN?
Vomiting and higher levels of anxiety reduce likelihood of recovery
Although it is not surprising that vomiting and higher levels of anxiety are associated with a lower likelihood of recovery, it is interesting to hypothesize about why vomiting, as opposed to other compensatory behaviours, and anxiety, as opposed to other personality/temperament traits were more predictive.
Though it is unclear, the authors hypothesize that vomiting mt might be “related to higher levels of psychological disturbance seen in individuals with AN and purging.” These disturbances can interfere with treatment.
As for anxiety, food restriction and exercise are thought to have an anxiety-reducing (anxiolytic) effect (I’ve talked about this a lot). The higher the levels of anxiety and the more effective restriction/exercise/purging is at removing the anxiety, the stronger the negative reinforcement to continue using those behaviours to decrease the anxious state.
Moreover, anxiety disorders tend to run in families with eating disorder patients and occur prior to onset of AN, suggesting that anxiety might increase the risk of developing an ED and subsequently decrease chances of recovery. I would also think that it suggests there is genetic overlap between factors that predispose individuals to AN and anxiety disorders. (I’ve talked in more depth about the links between AN and anxiety here.)
What about impulsivity?
What’s more interesting is that impulsivity was associated with a higher likelihood of recovery. You might be wondering what I meant by “the relationship… varied through time.” Zerwas et al. explain: :at onset, impulsivity was positively associated with recovery, but as duration of AN increased, the positive association between impulsivity and recovery declined.”
Previous studies have found impulsivity to be associated with a negative outcome, so the generalizability of the data in this study are uncertain. Is it just fluctuation? Might it be because of the different ways the authors of the studies measured impulsivity?
Fichter et al.’s (2006) measure of impulsivity included ratings of auto-aggressive behavior, shoplifting of nonfood articles, and promiscuity. Impulsivity in the present study was measured with the BIS, which may capture different psychological constructs. Impulsivity as measured by the BIS may be associated with recovery from AN because it tempers the rigidity and intractability often associated with AN and could encourage experimenting with healthier eating behaviors, whereas Fichter et al.’s (2006) measure might more appropriately index sensation-seeking behaviors.
MY OWN UNPOLISHED THOUGHTS…
I thought it was interesting that vomiting was a negative prognostic factors and impulsivity was a positive factor, given that impulsivity is associated with bingeing and purging behaviours. Which led me to think: in this study, the authors largely excluded patients that had binge eating behaviours. Which means that most of the individuals who engaged in self-induced vomiting were not bingeing and purging, they were just purging.
To me, bingeing and purging is very different from purging a normal meal. Anecdotally, I have noticed that those with AN who restrict and purge, but do not binge, seem to be more rigid in their thinking, and often more anxious. Those who binge and purge seem to fare better, overall. (I’m making generalizations and hypothesizing, so please don’t take it to mean that this applies to everyone.) Perhaps in this study, since those who binge/purge were largely excluded, impulsivity became an important variable in predicting recovery, for the reasons quoted above.
Is binge eating a positive predictive factor in recovery from anorexia nervosa? Indeed, is the shift from restricting to bingeing and purging type AN and perhaps subsequently to bulimia nervosa, a positive predictive factor in recovery over the long term? Surprisingly, I haven’t researched this question. I want to say ‘Yes’ but I hesitate because I might be overly reliant on my personal experiences.
As always, it is important to mention the strengths and limitations of the study so that we are careful not to overinterpret the findings. Some strengths: large sample size, strict definition of recovery, multisite study, varied sources of participants (more representative of the AN population as a whole).
There are some weaknesses. Retrospective studies have pros and cons, and one of the cons is that we are generally pretty crappy at accurately describing how we felt and what we thought. There’s also hindsight bias, recall bias, and generally skew events. This is particularly problematic when coloured by malnutrition and malnutrition-induced cognitive deficits. The authors also assumed that participants did not have a period of recovery during the duration of their ED (unless they were the 18.1% that were recovered at the time of the study). Naturally, if this assumption is incorrect, it may pose some problems to the interpretation of the data.
Anyway, I’d love to hear your thoughts! Leave a comment and let me know what you think about these data.
Zerwas, S., Lund, B., Von Holle, A., Thornton, L., Berrettini, W., Brandt, H., Crawford, S., Fichter, M., Halmi, K., Johnson, C., Kaplan, A., La Via, M., Mitchell, J., Rotondo, A., Strober, M., Woodside, D., Kaye, W., & Bulik, C. (2013). Factors associated with recovery from anorexia nervosa Journal of Psychiatric Research DOI: 10.1016/j.jpsychires.2013.02.011