Psychiatric Comorbidity
Two-thirds of patients with anorexia nervosa and three-fourths of patients who meet diagnostic criteria for both anorexia nervosa and bulimia nervosa are also diagnosed with at least one mood disorder on presentation. Of patients with anorexia nervosa, up to 60% are diagnosed with major depression and about 33% with anxiety disorders at intake. Obsessive-compulsive disorder accounts for one-half of the associated anxiety disorders, but generalized anxiety disorder, phobias, and panic disorder are also common. The lifetime risk of affective disorder in patients with anorexia nervosa is reported to range from 84% to a nearly universal 98%.

Personality disorders are diagnosed in at least 20% and as many as 80% of patients with anorexia nervosa. Patients with the restricting type of anorexia nervosa tend to exhibit Cluster C (anxious) personality disorders, such as avoidant, dependent, and compulsive, with Cluster A (odd) disorders, such as paranoid and schizoid, sometimes present. The Cluster B (dramatic) personality disorders, such as borderline, histrionic, and narcissistic, tend to be present only in patients with anorexia nervosa binge eating/purging type. Patients with anorexia nervosa also present a lifetime risk of alcohol, amphetamine, and other substance abuse problems, which may be concurrent with the eating disorder.

In addition, starvation is known to produce psychiatric symptoms such as dysphoria, anxiety, obsessiveness, and hyperactivity, which complicate the diagnosis of comorbidity. This phenomenon further underscores the importance of ending starvation and reversing malnutrition as the essential first steps in treating anorexia nervosa.