Anorexia Nervosa and Obsessive-Compulsive Disorder

Ten to 40 percent of patients with anorexia nervosa are diagnosed with obsessive-compulsive disorder. Likewise, 11 percent of patients with a primary diagnosis of obsessive-compulsive disorder have a coexisting eating disorder. Furthermore, first-degree relatives of persons with anorexia nervosa have an approximately three to five fold elevated risk of obsessive-compulsive disorder compared with relatives of healthy controls.

The above data suggest the presence of a genetic link between these disorders. This link has also been supported by a genome-wide association study (GWAS), which found a genetic correlation between anorexia nervosa and obsessive-compulsive disorder.

However, in some patients with anorexia nervosa, the diagnosis of obsessive-compulsive disorder is often made in response to typical eating disorder features, such as the adherence to eating rituals and/or excessive and compulsive exercising, and is therefore misplaced.

Eating disorder features are often confused as expressions of obsessive-compulsive disorder.

Eating rituals are common in people with anorexia nervosa and are often accentuated by caloric restriction and being underweight. These behaviors were even reported in the Minnesota Starvation Experiment participants, who underwent a prolonged period of semi-starvation without having any features of eating-disorder psychopathology. Only later were these features recognized as “starvation symptoms” by clinicians when they noted their presence in people with anorexia nervosa. The most frequent eating rituals observed are stirring food, separating the food to be eaten, counting bites, cutting food into geometric shapes, cutting food into small pieces, chewing for a long time, taking long breaks between bites, and eating extremely slowly.

Excessive and compulsive exercising is also a common feature of people with eating disorders, particularly those of low weight. In a sample of patients admitted to my unit, for example, excessive exercising was observed in 45.5% of cases, with the highest prevalence (80%) in those diagnosed with restrictive anorexia nervosa. Excessive and compulsive exercising has two distinctive characteristics: (i) its duration, frequency, and intensity exceeds what is necessary to obtain health benefits and increases the risk of producing physical damage; and (ii) it is associated with a subjective sense of being forced or compelled, taking priority over other day-to-day activities and causing guilt or anxiety if postponed.

Eating rituals and excessive and compulsive exercising is a direct expression of the core psychopathology of eating disorders (i.e., the overvaluation of shape, weight, eating, and control). These behaviors are used to manage concerns about shape, weight, and eating control.

However, these two specific features of the eating-disorder psychopathology are often considered features of an obsessive-compulsive disorder, given the rigidity and persistence with which they are applied.

To prevent misunderstanding, the DSM-5 clearly states, in criterion D of the obsessive-compulsive disorder diagnosis, that the disorder should not be explained by the symptoms of other mental disorders, which include ritualized eating behaviors of eating disorders. In addition, in the “differential diagnosis” section, the DSM-5 specifies that obsessive-compulsive disorder can be distinguished from anorexia nervosa because, in the former, obsessions and compulsions are not limited to concerns about shape and weight.

Another element that distinguishes the two psychopathologies is the ego-syntonic nature of the patient’s concerns. Specifically, patients with eating disorders perceive preoccupation with food and eating as functional to the control of weight and body shape. In contrast, those with the obsessive-compulsive disorder tend to judge their obsessions as intrusive and harmful.

The above considerations underscore the importance of carefully assessing the nature of the disordered behavior in order to achieve an accurate diagnosis and how merely relying on observation of symptoms is frequently flawed and misleading. Furthermore, a misdiagnosis of obsessive-compulsive disorder exposes patients to inadequate psychological and psychopharmacological treatments that can aggravate and maintain the eating disorder.

When obsessive-compulsive disorder coexists with an eating disorder

When obsessive-compulsive disorder does coexist with an eating disorder, and the obsessions and compulsions are not solely focused on concerns about food and eating, the question arises regarding when to address the two disorders.

The obsessive-compulsive disorder does not generally interfere with treating eating disorders but does not respond to its treatment. It must therefore be recognized, and a decision made on when to address it with psychological treatment. This should be before or after, but preferably not simultaneously. In most cases, clinicians address the eating-disorder psychopathology first because, as seen in the Minnesota Starvation Experiment, being underweight accentuates the frequency and intensity of obsessions. However, it is common to combine a psychopharmacological treatment for obsessive-compulsive disorder with a psychological intervention for the eating disorder.

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Much more problematic, though rare, are cases of obsessive-compulsive disorder in which obsessions and compulsions influence the patient’s eating and, therefore, act to maintain the eating-disorder psychopathology. In such cases, the persons tend to report that eating rituals are used to manage some obsessions not related to the control of shape and weight (e.g., “If I do not cut food into geometric shapes, something bad will happen”; “If I eat the last bite, this moment will disappear forever and I will never get it back”; “Something irreparable could happen if I eat quickly”; “If I eat some foods, I will be contaminated”). In these cases, the two disorders should be treated simultaneously, although this option is complex and requires a therapist with the skills to simultaneously address the two disorders.

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