Platelet MAO activity in anorexia nervosa patients with and without a major depressive disorder.

Platelet MAO activity was determined in 33 anorexia nervosa patients. A subgroup of 15 patients who met Research Diagnostic Criteria for a concomitant major depressive disorder were found to have, both initially and after 5 weeks of treatment, significantly lower mean platelet monoamine oxidase (MAO) activity than 28 matched normal control subjects. In contrast, mean platelet MAO activity in the patients who did not meet criteria for major depressive disorder was similar to values in control subjects. The authors found that significantly more depressed patients had low MAO activity compared with nondepressed patients and controls. Platelet MAO activity may be useful in discriminating among subtypes of anorexia nervosa patients.