Elevated brain serotonin transporter availability in patients with obsessive-compulsive disorder

Background: A central serotonergic dysfunction is considered to be involved in the pathophysiology of obsessive-compulsive disorder (OCD). The aim of this study was to investigate the serotonin transporter availability in patients with OCD as an in vivo marker of the central serotonergic system. Methods: Nine unmedicated (7 drug-naive) patients with OCD and 10 healthy control subjects were included and received single photon emission computed tomography (SPECT) 20.75 +/- 1.51 hours after injection of a mean 147.20 +/- 6.74 MBq [I-123]-2beta-carbomethoxy-3beta-(4-iodophenyl)tropane ([I-123]beta-CIT). As a measure of brain serotonin transporter availability, a ratio of specific-to-nonspecific [I-123]beta-CIT binding for the midbrain-pons (V-3 = [midbrain/pons-occipital]/occipital) was used. Results: Mean specific-to-nonspecific ratios showed a 25% higher midbrain-pons [I-123]beta-CIT binding in the patients as compared with healthy controls (2.26 +/- .37 vs. 1.81 +/- .23, p < .01). The difference remained significant after adjustment for clinical variables and controlling for age and gender. Stratification of the patients according to onset of the disorder revealed significant differences between controls and patients with early (childhood, adolescence) but not late (adult) onset of OCD. Conclusions: The study provides evidence of a serotonergic dysfunction in patients with OCD and suggests a serotonergic component in the pathophysiology of the disorder.