Shiraz E-Med J. 2014 July; 15(2): e20590. Published online 2014 July 10. Research Article Assessment of Cognitive Inhibition in Patients with Obsessive-Compulsive Disorder Arash Mani 1 ; Ali Sahraian 2,* ; Zohreh Fouladivanda 2 1 Cognitive Neuroscience, Research Centre For Psychiatry and Behavioral Sciences, Department of Psychiatry, School of Medicine, Shiraz University of Medical Sciences, Shiraz, IR Iran 2 Research Centre for Psychiatry and Behavioral Sciences, Department of Psychiatry, School of Medicine, Shiraz University of Medical Sciences, Shiraz, IR Iran *Corresponding Author: Ali Sahraian, Research Centre for Psychiatry and Behavioral Sciences, Department of Psychiatry, School of Medicine, Shiraz University of Medical Sciences, Shiraz, IR Iran. Tel: +98-711-6279319, Fax: +98-711-6279319, E-mail: sahraian@sums.ac.ir Received: March 6, 2014; Revised: March 10, 2014; Accepted: March 22, 2014 Background: Obsessive-compulsive disorder (OCD) is not only one of the most prevalent psychiatric disorders, is also one of the most disabling medical disorders with some cognitive deficits, like poor cognitive inhibition. Objectives: The main purpose of the present study is to compare cognitive inhibition between patients with OCD and a healthy control group. Patients and Methods: This was a cross-sectional study, performed on 20 patients with OCD and 20 patients in the control group, selected with convenience sampling method, from outpatients and inpatients. They completed a computerized cognitive inhibition task and the Maudsley Obsessional-Compulsive Inventory (MOCI). Data were analyzed by SPSS and a P-Value less than 0.05 was considered significant. Results: The results indicated that patients and control groups were equal according to sex and education and there was no significant difference. Also, the results show that the difference in negative prime between the two groups was significant, although the differences in positive prime and neuter stimuli were non-significant. Conclusions: According to cognitive inhibition deficits in patients with obsessive–compulsive disorder, it seems that in protocol treatment, patients should be provided with instructions, in the field of cognitive rehabilitation. Keywords:Cognitive Inhibition; Neuropsychology; Executive Function Implication for health policy/practice/research/medical education: The main purpose of the present study is to compare cognitive inhibition between OCD and healthy control. Copyright © 2014, Shiraz University of Medical Sciences; Published by Safnek. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 1. Background Obsessive-compulsive disorder (OCD) is not only one of the most prevalent psychiatric disorders, is also one of the most disabling medical disorders. Today, it is referred to as a neuropsychiatric disorder, mediated by specific neuronal circuitry, closely related to neurological condi- tions (1). According to DSM IV criteria, OCD is character- ized by intrusive thoughts or images (obsessions), in- creasing anxiety and also repetitive or ritualistic actions (compulsions), decreasing anxiety (2). Patients with this disorder are thought to suppress or neutralize annoying thoughts they are facing. These intrusive and obsessive thoughts, contrary to the patients’ will, frequently ap- pear with failure to inhibit irrelevant information (3). Cognitive deficits could function as intermediate vari- ables, between neurobiological abnormalities and OCD symptoms (4). Different studies have focused on involve- ment of cortico-striatal-thalamic-cortical circuits in OCD patients and have mainly supported imaging researches and also the results of the developmental studies (5, 6). Accordingly, neuropsychological deficit is common among these patients. Involvement of the cortical region, especially in the frontal lobes, (7) proposes a possible ex- ecutive function (EF) impairment. Executive function is defined as a set of cognitive skills, necessary to plan, mon- itor and execute a sequence of goal-directed complex ac- tions (8). Assessment of the ability to inhibit, through these cognitive skills, known as EFs, was the main goal of the present study. Cognitive inhibition means slowing the response to an item, currently neglected. Indeed, it refers to delay or increase the errors, when responding to an item that had been overlooked in the past (3). Tra- ditionally, cognitive inhibition was evaluated by priming and shifting tasks. Shifting and mental flexibility, as parts of EF, are necessary for humans’ interactions with the environment. In the literature on shifting and priming effects, there are two situations; in the first case, the cor- rect and incorrect features of stimuli features are repeat- ed across two trials, called positive priming (PP) and the second case is when the correct and incorrect features are switched, known as negative priming (NP) (9). The effect of priming task (negative or positive) is con- troversial, for example; Amir, Cobb and Morrison did a research on 19 patients with OCD and 19 healthy controls, evaluating the cognitive inhibition. The results demon-