The paper discussed here is comparative cognitive profiles of obsessive-compulsive disorder (OCD) and schizophrenia by Vera Martin and colleagues. The researchers set out to identify differences in cognitive profiles between 19 people with schizophrenia, 19 people with OCD and 19 controls. The average age of the subjects was around 30 and they had received an average of 16 years of education. German translations of rating scales were used. Subjects were administered a battery of tests including the PANSS, structured clinical interview for DSM-IV and various neuropsychological tests including the Weschler Adult Intelligence Scale – Revised and the Weschler Memory Scale Revised. Some of the neuropsychological test subscores were aggregated to produce categories such as working memory and the internal reliability of these categories was tested using cronbach’s alpha scores. A number of different statistical tests were used to examine the relationships between variables.
The main findings were that both people with OCD and Schizophrenia didn’t perform as well as controls on visual memory tasks and verbal memory tasks – although the former groups didn’t differ significantly from each other. People with schizophrenia performed significantly worse than people with OCD who in turn performed significantly worse than controls on a test of simple attention. However dose of antipsychotic was significantly correlated with attention scores in the schizophrenia group.
Interestingly when controlling for depression (BDI scores) simple attention differences between the schizophrenia and OCD group remained but there were no differences between the OCD group and control group. OCD and psychosis severity however didn’t influence the scores on the neuropsychological tests.
On reading this paper it struck me that the depression scores seemed to be a mediator of the cognitive difficulties in OCD and that medication was partly mediating the simple attention scores in schizophrenia. The remaining differences that needed to be explained were the visual and verbal memory performances in schizophrenia. The authors point out that the findings suggest differences between the cognitive profiles in people with schizophrenia and OCD.
Given the overlap that can sometimes occur with OCD and psychosis, studies of this kind are important in pushing understanding of this area forward.
The authors had discussed the mediating effect of depression in people with OCD at length and the medication relation to simple attention. It was the visual and verbal memory difficulties that probably need explaining (just to avoid any ambiguity).
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