Eating disorder (ED) is a quite complex syndrome.
ED and Obsessive Compulsive Disorder (OCD) have some common characteristics, it makes us confused. Both happen in young adult ages. Cognitive distortions are the core in both diseases. And behaviors in both patients are often extremely odd, so that we hardly understand.
The author of this article below had a son who suffered from OCD, which was misdiagnosed as ED.
PsychCentral: OCD vs. Eating Disorders
I agree with most of the content by the author. OCD is sometimes difficult to distinguish from ED. I have some similar experiences. In many cases, the patients had to be hospitalized due to excessively low body weight. We suspected they were suffering from anorexia nervosa. However, the true reason they hesitated to eat was an irrational thought, such as they get ill when they eat something unless they wash the hands properly in advance. In contrast, it is rare that we misdiagnose an ED as OCD.
By the way, I am wondering about the gender rate of patients with ED. In DSM-5, the female/male rate of prevalence is estimated at 10:1 in anorexia nervosa and bulimia nervosa. On the other hand, male patients with binge eating disorder are nearly as many female patients. Some studies support this description. The data in the US show that the female/male rate of all eating disorders are 2.5:1 in most of the states.
ANRED: Statistics: How many people have eating disorders?
ANAD: Eating Disorder Population by Gender in each State
In my experience, male Japanese patients with EDs are less than one-tenth of the female, at least in a clinical setting. I met more than one-hundred patients, but only 4 were male, of which one was diagnosed as obsessive compulsive personality disorder and another became schizophrenic soon after recovered from ED.
It is also under discussion whether AN and BN have a common root. It is no doubt that some AN patients change into BN as the therapy proceeded. DSM-5 has not proposed an answer to this question. I think that a few patients with AN have specific, maybe genetic or endogenic, factors which cause resistance to treatment. They have often poor prognosis. Other patients are reactive to cognitive behavioral therapy or other intervention. The other day, some of my colleagues attempted to distinguish the two types using blood analysis, but the result was not satisfactory.
ED is one of the most curious mental illnesses. The genesis of this disease is partially related to modern lifestyles. However, it cannot give the entire explanation of its pathology. Some patients need extremely intensive care. We have to be more skillful to deal with this complicated disorder.