Lower levels of whole blood serotonin in obsessive-compulsive disorder and in schizophrenia with obsessive-compulsive symptoms

It has been reported that some schizophrenic patients suffer from obsessive-compulsive symptoms (OCS), and clozapine treatment is quite often associated with an occurrence/increase of OCS in schizophrenic patients. The aim of the study was to explore whether differences would exist in the clinical symptomatology and the whole blood serotonin (5-HT) concentrations in patients with obsessive-compulsive disorder (OCD), schizophrenic patients with and without OCS (S + OCS, S − OCS), and clozapine-treated schizophrenic patients with and without clozapine-induced OCS (CLZ + OCS, CLZ − OCS). We found that S + OCS patients (n = 15) showed significantly lower scores on the Hamilton Anxiety Scale (HAMA), but similar levels of compulsions and obsessions using Yale-Brown Obsessive-Compulsive Scale (YBOCS) as compared to the patients (n = 35) with OCD. S + OCS patients scored significantly lower on the Positive and Negative Syndrome Scale (PANSS) but higher on the Hamilton Depression Scale (HAMD) compared with S − OCS patients (n = 19). However, CLZ + OCS patients (n = 15) suffered from dominant compulsions but fewer obsessions compared with the OCD and S + OCS patients. OCD, S + OCS and CLZ + OCS groups had significantly lower levels of whole blood 5-HT than did the healthy volunteers (n = 15), S − OCS and CLZ − OCS groups. It suggests that alterations in serotonin metabolism may be a common biological characteristic of OCS in OCD as well as in schizophrenia.