Psychiatry Research 69 (1997) 9-1.5 zyxwvutsrqponmlkjihgfedcbaZYXWVUT PSYCHIATRY RESEARCH Plasma tryptophan levels and tryptophan/neutral amino acid ratios in obsessive-compulsive patients with and without depression Laura Bellodi”, Stefano Erzegovesi, Laura Bianchi, Valentina Lucini, Roberta Conca, Adelio Lucca zyxwvutsrqponmlkjihgfedcbaZYXWVUTSR Department zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA of Neuropy chiatric Sciences, Istituto Scientifico Ospedale San Raffaele, University of Milan School of Medicine, Via Luigi Prinetti 29, 20127 Milan, Italy Received 27 December 1995; revised 18 July 1996; accepted 4 November 1996 Abstract We have studied fasting plasma tryptophan (TRP) levels and tryptophan/large neutral amino acid (TRP/LNAA) ratios in 12 patients with obsessive-compulsive disorder (OCD) and 12 patients with OCD and a coexisting current diagnosis of major depressive disorder (OCD-MDD). Assessments were made at baseline and after 6 weeks of treatment with fluvoxamine. OCD-MDD patients had significantly lower baseline TRP levels and TRP/LNAA ratios than OCD patients. After 6 weeks of fluvoxamine treatment, OCD-MDD patients had significant increases in plasma TRP and TRP/LNAA ratio, whereas OCD patients had non-significant decreases. Our data suggest that a major depressive syndrome could be a state variable affecting the changes in plasma TRP and TRP/LNAA ratio in OCD patients. 0 1997 Elsevier Science Ireland Ltd. Keywords: Tryptophan; Amino acids; Serotonin; Fluvoxamine 1. Introduction patients with obsessive-compulsive disorder (OCD) led to the ‘serotonin hypothesis’ of OCD The fact that serotonin (5HT) reuptake inhibi- (Goodman et al., 1989a; Pigott et al., 1990; Barr tors reduce obsessive-compulsive symptoms in et al., 1992; Smeraldi et al., 1992). Recent studies with 5HT agonists and/or antagonists as phar- macological probes (Zohar et al., 1987; Hollander * Correspondence author. Tel.: + 39 2 26433315; fax: + 39 2 et al., 1992) have provided additional support for 26433265; e-mail: bellodl@rsisi.hsr.it. the role of the S-HT system in the pathogenesis 01651781/97/$17.00 6 1997 Elsevier Science Ireland Ltd. All rights reserved. PIlSO165-1781(96)02961-7