Background: Obsessive compulsive disorder (OCD) is a highly heritable neuropsychiatric disorder. Attempts to elucidate contributing genes have met with limited success. Intermediate markers of brain

The aim of this study is to test the hypothesis that coadjuvant treatment with SSRI and topiramate would improve the outcome of patients with comorbid OCD and impulsive behaviour disorders. Methods: We will describe two clinical cases admitted to our Psychiatric Hospitalization Unit. Case 1 is a 39 years old female diagnosed with OCD, borderline personality disorder and alcohol dependence and case 2 is a 38 years old male with OCD, mixed personality disorder and cocaine abuse. Results: Treatment with topiramate (range dosage: 250-400 mg/ daily) as well as SSRI (paroxetine 40 mg/daily-case 1; sertraline 200 mg/daily-case 2) improved affective instability and impulsive symptoms in both patients. Topiramate was well tolerated without important side effects. Conclusions: Topiramate could be an interesting alternative in the coadjuvant treatment of OCD with impulsive features.

Background: Obsessive compulsive disorder (OCD) is a highly heritable neuropsychiatric disorder. Attempts to elucidate contributing genes have met with limited success. Intermediate markers of brain

dysfunction (cognitive endophenotypes) may help focus the search for genetic contributions. Such markers should be present in people at risk of developing OCD in the absence of clinical symptoms. In prior work, OCD patients showed impairment on tests of response inhibition and cognitive flexibility (Chamberlain et al., 2005, 2006). Methods: First-degree relatives of OCD patients, patient probands, and matched healthy volunteers without a family history of OCD undertook neuropsychological assessment (n¼20 per group). Results: Compared to matched controls without a family history of OCD, unaffected first-degree relatives of OCD patients showed impaired response inhibition (p<0.05) and cognitive flexibility (p<0.05). These deficits were comparable to those in the patients themselves. Conclusions: Brain-based cognitive markers of inhibitory functions may be of utility in the search for OCD endophenotypes. Examination of relationships between these abnormalities, genetics, and structural/functional brain changes, will help to elucidate aetiological contributions to OCD and putative spectrum disorders.