Following at
least 5 weeks of successful treatment with serotonin reuptake inhibitors
(SRI), 15 patients diagnosed with obsessive-compulsive disorder received
2 tests 7-10 days apart, a tryptophan-containing amino acid drink (control
nondepletion) and an amino acid drink without tryptophan (active depletion). Ratings before the drink were subtracted from
ratings 7 hrs. after the drink to obtain the drink effect for each of
the control and active drinks. The
change plotted above is the active drink effect minus the control drink
effect (adapted from Barr et al. - 4).