ELEVATED CEREBROSPINAL-FLUID LEVELS OF OXYTOCIN IN OBSESSIVE-COMPULSIVE DISORDER - COMPARISON WITH TOURETTES-SYNDROME AND HEALTHY CONTROLS

Background: Limited neurobiological data have implicated central argin ine vasopressin in the pathobiology of obsessive-compulsive disorder ( OCD). Based on twin, family genetic, and pharmacological studies, some forms of OCD are etiologically related to Tourette's syndrome. The ro le of arginine vasopressin and related compounds such as oxytocin in T ourette's syndrome has not been previously explored. Methods: To compa re cerebrospinal fluid (CSF) levels of arginine vasopressin and oxytoc in, we collected CSF at midday in a standardized fashion from a total of 83 individuals (29 patients with OCD, 23 patients with Tourette's s yndrome, and 31 normal controls). We also collected family study data on each subject to determine which subjects had a family history posit ive for Tourette's syndrome, OCD, or related syndromes. Results: In co ntrast to previous reports, we report similar concentrations of argini ne vasopressin for all three groups but increased oxytocin levels in p atients with OCD. Remarkably, this increase was observed only in a sub set of patients with OCD (n=22) independently identified as being with out a personal or family history of tic disorders (P=.0003). In this s ubgroup of patients, the CSF oxytocin level was correlated with curren t severity of OCD (n=19, r=.47, P<.05). Conclusions: A possible role f or oxytocin in the neurobiology of a subtype of OCD is suggested by th e elevated CSF levels of oxytocin and by the correlation between CSF o xytocin levels and OCD severity. These findings reinforce the value of family genetic data in identifying biologically homogeneous (and perh aps more etiologically homogeneous) groups of patients with OCD. Toget her with emerging pharmacological data showing differential responsive ness to treatment of tie-related OCD vs non-tie-related OCD, these dat a also argue strongly for the incorporation of tie-relatedness as a va riable in biological and behavioral studies of patients with OCD.