Obsessive-Compulsive Disorder: Towards Better Understanding and Outcomes

Kenneth C. Kirkby

Disclosures

Curr Opin Psychiatry. 2003;16(1) 

In This Article

Neuropsychology

Exploration of the links between the most prominent symptoms of OCD, the distorted obsessional thoughts and compulsive behaviours, and presumptive underlying differences in the fine structure and function of the brain, is a fertile field for neuropsychological investigations. Comparisons of OCD and other conditions are informative. Spitznagel[46*] compared orbitofrontal and dorsolateral patterns of frontal lobe dysfunction implicated in subjects with OCD and schizotypy respectively, in subjects with either condition and in a mixed group with OCD and schizotypy. Results confirmed orbitofrontal type problems, such as difficulty changing cognitive set, in the OCD group only. Following a similar line of thought, Nielen[47*] compared a decision making task in drug-free OCD and control subjects with negative results. Cavedini[48*] on the other hand reported decision-making impaired in OCD compared to controls and panic subjects, with impairment predictive of a poorer pharmacological response for OCD. Jurado[49*] assessed memory for temporal order as well as a 'feeling-of-doing' judgement, finding these impaired in OCD; in a second study incidental memory for frequency was impaired in OCD.[50*]

Another interesting aspect of memory is negative priming, whereby ignoring a particular stimulus can hamper subsequent attended processing of the same stimulus. Negative priming is reduced in OCD, consistent with reduced inhibitory function. This is further explored in a study comparing schizophrenia, OCD and controls, which demonstrated differences in negative priming in OCD subtypes of checkers versus non-checkers, with differences varying with response-stimulus interval.[51**] A related tack is that of directed forgetting, based on evidence that OCD patients show impaired ability to forget negative material, with limited further support from a study comparing OCD and anxious controls.[52*]

Controlled studies such as these clarifying what instruments distinguish between OCD and control groups, and better characterizing the integrity of frontostriatal pathways, will assist in teasing out the neuropsychological puzzle of OCD. In a good proportion of the neuropsychological studies cited in this review, the researchers are testing two dozen OCD subjects or more against controls with other and/or no disorder, which is a significant recruitment task. Such sample sizes permit a sober analysis of the results and some confidence in their replicability.

Fontenelle[53*] examined deficits in set shifting as indexed by categories completed and perseverative errors and found these to be related to positive treatment response to SSRI. The possible effects of psychotropic medications per se on cognitive function in OCD is investigated by Mataix-Cols[54**] in medicated and unmedicated subjects of comparable symptom severity. SSRI get a clean bill of health and some interesting interactions between SSRI and benzodiazepines are reported which require elucidation. The lack of cognitive change attributable to SSRI is an important finding since many studies are undertaken in mixed OCD samples with some participants taking these medications. Another important confound in studies of cognition in OCD is comorbid depression. Moritz[55*] used a median split based on Hamilton depression scores to analyse cognitive deficits on executive function tests such as Wisconsin Card Sorting Test, in OCD subjects. Higher depression scores were associated with greater deficits, sounding a note of caution in interpreting the provenance of deficits commonly observed in OCD. Basso[56*] takes a similar approach in a smaller sample, using a regression analysis and the depression score from the Minnesota Multiphasic Personality Inventory as a predictor and reports a similar finding for frontal lobe type tests, but no effect of depression on sensory-motor deficits in OCD. Custom designed studies using samples with and without comorbid major depression would be needed to further resolve this question.

Johannes[57**] examined event-related potentials to a choice reaction time task and found that OCD subjects showed reduced P3b latency and amplitude enhanced error-related negativity compared to controls. This is interpreted as being quicker to evaluate targets and showing greater 'action monitoring'.

Some of these studies abut and inform phenomenological approaches. Thus Pelissier[58*] examined inductive and deductive reasoning in a small comparison of OCD, generalized anxiety disorder and non-anxious controls. OCD subjects showed differences on some tasks in probabilistic reasoning and greater conviction, echoing some of the cognitive distortions found in OCD. At the other end of the spectrum is research into the neurology of OCD, specifically in terms of brain lateralization. Siviero[59*] reports a high rate of both left eye preference and left hand preference in OCD, compared to dyslexia and controls.

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