1. ¹Department of Psychiatry, Medical University of Vienna, Vienna, Austria
2. ²Department of Public Health, University of Veterinary Medicine, Vienna, Austria
3. ³Department of Anesthesiology, Medical University of Vienna, Vienna, Austria
4. ⁴Department of Nuclear Medicine, Medical University of Vienna, Vienna, Austria
5. ⁵Department of Statistics and Mathematics, Vienna University of Economics and Business Administration, Vienna, Austria

Correspondence: Assistant Professor W Zitterl, Department of Psychiatry, Medical University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria. Tel: +43 1 40400 3568; Fax: +43 1 40400 3560; E-mail: werner.zitterl@meduniwien.ac.at

Received 9 June 2005; Revised 6 October 2006; Accepted 25 October 2006; Published online 27 December 2006.

Abstract

Numerous findings indicate alterations in brain serotonin systems in obsessive-compulsive disorder (OCD). We investigated the in vivo availability of thalamus–hypothalamus serotonin transporters (SERT) in patients with DSM-IV OCD who displayed prominent behavioral checking compulsions (OC-checkers). Four hours after injection of [¹²³I]-2-carbomethoxy-3-(4-iodophenyl)tropane ([¹²³I]--CIT), single photon emission computed tomography (SPECT) scans were performed in 24 medication-free non-depressed OC-checkers and 24 age- and gender-matched healthy controls. For quantification of brain serotonin transporter availability, a ratio of specific to non-displaceable [¹²³I]--CIT brain binding was used (V"₃=(thalamus and hypothalamus-cerebellum)/cerebellum). Drug-free non-depressed OC-checkers showed an 18% reduced brain serotonin transporter availability in the thalamus and hypothalamus, as compared with healthy control subjects (1.380.19 vs 1.690.21; p<0.001). There was a strong negative correlation between severity of OC symptomatology (Y-BOCS scores) and SERT availability (r=-0.80; p<0.001). Moreover, we found a significant positive correlation between illness duration and serotonin transporter availability (r=0.43; p<0.05). This first report of significantly reduced [¹²³I]--CIT binding in the thalamus–hypothalamus region in OC-checkers suggests reduced brain serotonin transporter availability, which is more pronounced with increased severity of OC symptomatology and short duration of illness. The results provide direct evidence for an involvement of the serotonergic system in the pathophysiology of OCD.