Some evidence exists to suggest that serotonin 5-HT2A receptor function is altered in anorexia nervosa and bulimia nervosa. In order to further investigate the 5-HT2A receptor in eating disorders, platelet [H-3]lysergic acid diethylamide ([H-3]LSD) binding was studied in ten patients with anorexia nervosa, 23 patients with bulimia nervosa and 33 healthy controls. At admission, B-max for platelet [H-3]LSD binding was significantly higher both in the anorexia nervosa group (30.6 +/- 4.2 fmol/mg protein; mean +/- S.D.) and in the bulimia nervosa group (30.8 +/- 7.6 fmol/mg protein) than in the control group (23.5 +/- 6.3 fmol/mg protein; p=0.01 and p=0.003, respectively). K-d was borderline significantly higher among anorexics (median 1.45 nhl) and significantly higher among bulimics (median 1.66 nM) than among controls (median 0.95 nM; p=0.05 and 0.003, respectively). The Global Assessment of Functioning score and the body mass index were both significantly negatively correlated to k(d) (r=-0.40; p=0.03 and r=-0.41 p=0.03, respectively), but not to B-max. The present study indicates that patients with anorexia nervosa as well as patients with bulimia nervosa have an enhanced 5-HT2A receptor binding and provides further evidence for a serotonergic dysfunction in eating disorders. (C) 1999 Elsevier Science B.V. All rights reserved.