COMT polymorphisms and Mini-Mental State Examination performance in schizophrenia

Abstract

Introduction Individuals with schizophrenia have cognitive deficits which have been associated with genetic polymorphisms such as those of the gene coding for the catechol-O-methyltransferase enzyme (COMT-[rs4680]). Aim To examine the relationship of schizophrenia diagnosis and COMT-[rs4680] polymorphisms with the performance on the Mini-Mental State examination (MMSE). Patients and methods Ninety-two individuals with schizophrenia and 29 healthy controls were tested on the MMSE. COMT polymorphisms were characterized using the Restriction Fragment Length Polymorphisms method from DNA isolated from peripheral blood sample lymphocytes. Hierarchical linear regression analysis was used to examine the COMT polymorphisms X diagnosis interaction and the effects on MMSE scores, controlling for age and education. Results Individuals with schizophrenia versus healthy controls had a mean age of 43.69 (standard deviation [SD]=9.71) versus 43.79 (SD=7.80) years and mean education of 10.92 (SD=3.42) versus 12.82 (2.91) years. The two groups significantly differed in education (Mann-Whitney z=2.55, P =0.011). We found no evidence that COMT polymorphisms moderated any effect of diagnosis on MMSE or that they are associated with MMSE performance. Individuals with schizophrenia had lower MMSE scores than controls (mean difference=1.676; 95% Confidence Interval=0.499, 2.85; t =2.822, df=115; P =0.006). Conclusion Schizophrenia patients have lower MMSE scores controlling for the effect of age and education. COMT polymorphisms are not associated with MMSE scores.