Binge-Purge Anorexia vs Bulimia: what’s the difference?
It has now been three years since the new Diagnostic and Statistical Manual of Mental Disorders (DSM-5) was published and it’s time for an update to previous blogs on this topic (which have been replaced by this update).
Many people say: “I used to have anorexia and then I developed bulimia,” or “She has anorexia and bulimia.” These statements are not accurate, and stem from a common misperception that any purging (vomiting) means a patient “is bulimic” or “has bulimia.” More correctly, an individual either has anorexia nervosa, bingeing and purging subtype, or they have bulimia nervosa.
So why does it matter? Diagnosis is as important to get right in brain disorders (mental illnesses) as in disorders of other organ systems. It matters as much as it matters to differentiate between pneumonia and bronchitis. Both are illnesses of the lung with cough and fever, but each will have a slightly different natural history, treatment, and, sometimes, prognosis.
How these diseases are described by the DSM-5
The DSM-5 reports a prevalence of anorexia nervosa among females of 0.4% with a 10:1 female to male ratio and of bulimia nervosa of 1-1.5%, again with a 10:1 female to male ratio. Well, maybe. But they also say that these illnesses “rarely” present before puberty. This, I think, will change in future editions. With more attention paid to pediatric patients, we may see a softening of the ratios reported between males and females, for example. With a better understanding of the genetics and epigenetics of these illnesses, who knows what will change?
Importantly, perhaps, patients with bulimia nervosa tend to be of normal body weight or even higher than normal body weight. Their illness is characterized by episodes of bingeing (eating large amounts of food within a short period of time and a sense of loss of control) followed by compensatory behaviors, typically vomiting. Patients with bulimia nervosa may occasionally fast for a day or two, but do not have the characteristic long term weight suppression of those with anorexia nervosa. Patients with anorexia nervosa who display bingeing and/or purging behaviors will have long term weight suppression as part of their illness.
A few unanswered questions
But none of this answers a few of my own questions – and perhaps yours. Does a patient with bingeing and purging anorexia nervosa whose body weight has cycled and who is now of average (or even higher than average) body weight now have bulimia nervosa? Doesn’t make sense to me.
What happens when a person who has had long years of restricting anorexia nervosa begins to binge and purge? Does one form “morph” into the other? I don’t know the answer to that, but again it doesn’t make sense to me. There is a large (and tedious) body of mental health literature discussing the differences in temperament between “restrictors” and “purgers”.
Many therapists will tell you that their patients with restricting forms of the illness tend to be more tightly wound, more “restricted,” in their affect: they don’t smoke or drink or engage in risky behaviors, whereas those with purging seem be temperamentally more impulsive. This absolutely reflects our experience, as well. Since temperament is fairly robust (i.e. under genetic control), how could one “change into” the other?
Our experience – and a goal for treatment – of binge/purge anorexia at Kartini Clinic
So what are we Iooking at? I do see patients begin to purge who formerly only restricted (usually when they are older), but it seems to me to have a volitional or calculated base to it: the body will only tolerate severe caloric restriction for so long before the brain fights back and ups the neuropeptides that trigger food seeking.
“I found it harder and harder to restrict,” they report. Then panic ensues. How to get rid of the unwanted food they just ate? Vomit it up. And a cycle, possibly set into motion by the consequences of prolonged semi-starvation, begins to lead a life of its own, in essence imitating a purging eating disorder.
Until we have reliable biomarkers for these illnesses, a “lab test” if you like, we may never know the answer to these questions. And once the answers come, they may surprise us. Both forms of eating disorders may be related to the same biochemistry or entirely unrelated. They may only appear to be eating disorders, but actually be metabolic disorders or even delusional disorders which cause changes in ingestive behaviors. Whichever form these illnesses take, they need to be treated with respect. They need treatment and they need it now.
