An investigation of cognitive functioning and personality traits in obsessive-compulsive disorder, panic disorder, healthy controls and sub-clinical obsessive-compulsives

Obsessive-compulsive disorder (OCD) is a common psychiatric illness characterised by recurrent, intrusive thoughts and repetitive, stereotyped behaviours. There is converging evidence that OCD is associated with a specific cognitive deficit related to organising and manipulating information in working memory. There is also evidence that OCD is associated with certain pre-morbid personality traits. However, further research is needed to elucidate whether these cognitive deficits and personality traits are specific to OCD or are present in other anxiety disorders and/or individuals with sub-clinical levels of obsessive-compulsive (OC) symptoms. In this thesis, 20 OCD patients were compared to 20 patients with panic disorder, 20 subjects with sub-clinical OC symptoms and 20 healthy control subjects on tests of working memory and the Five-Factor Model of personality. To measure different aspects of working memory, participants completed three delayed matching-to-sample (DMS) tasks and two continuous performance working memory tasks (n-back tasks). The DMS tasks assessed the ability to actively maintain different types of information in working memory (irregular objects; geometric objects; spatial locations). The n-back tasks assessed the ability to update and temporally order verbal and spatial stimuli in working memory. The OCD patients were less accurate than the healthy control subjects on the memory trials of the spatial DMS task, the 3- back trials of the spatial n-back task, and the 2-back and 3-back trials of the verbal n-back task. The OCD patients were also less accurate than patients with panic disorder and sub-clinical OC subjects on the verbal 3-back task. The results indicated that OCD patients were impaired on cognitive tasks requiring the maintenance of spatial stimuli and the updating and temporal ordering of verbal and spatial stimuli in working memory. The OCD patients were not impaired on tasks requiring the maintenance of object information in working memory. To measure normal personality traits, subjects completed the Revised NEO Personality Inventory (NEO PIR). Compared to healthy controls, OCD patients reported being highly emotional and introverted, less open to new experiences, and lacking confidence in their own abilities. The OCD patients were similar to the panic disorder patients on most of the domains and facets of the NEO PI-R, however, they were distinguished by their lower openness to experiencing new activities, and being less diligent and purposeful. Compared to the sub-clinical OC subjects, OCD patients reported being more prone to feelings of depression, more vulnerable to stress, less likely to experience positive emotions, more humble and sincere and less able to carry tasks through to completion. Overall, the thesis provided further evidence that OCD patients are impaired on cognitive tasks requiring the organisation and manipulation of information in working memory. However, it is still unclear whether this deficit arises due to capacity constraints being exceeded in working memory systems, or some other executive dysfunction such as excessive error monitoring. Future research, combining neuropsychological testing with neuroimaging techniques, is required to better understand the neural mechanisms underlying the impaired performance of OCD patients on tests of working memory. The present thesis also found that normal personality traits - as measured by the NEO PI-R - were able to distinguish OCD patients from healthy controls, patients with panic disorder and individuals with sub-clinical levels of OC symptoms. The results have implications for sub-clinical OC research and the clinical management of OCD.