Background and objective: Cathecol-O-methyl transferase (COMT) is one of the most plausible susceptibility genes of schizophrenia risk. The main genetic variant (G158A or rs4680) studied is functional. It has been shown that G-A transition at COMT codon 158 makes COMT more thermolabile and less active at physiological temperature. Genetic variants in the P2 promoter have been suggested to cause alterations in brain COMT protein levels. A variant in the P2 promoter (-278A/G or rs1800706) has recently been associated with psychotic disorders. We studied whether polymorphisms in COMT (G158A, -278A/G) are risk factors for schizophrenia in a Spanish population.
Patients and method: 243 subjects diagnosed of schizophrenia and related disorders following the DSM-IV criteria and 291 hospital-based controls participated in an association study.
Results: The heterozygotes for the COMT -278A/G polymorphism showed a 60% reduction in the schizophrenia risk (p = 0.009). No significant differences were observed between the other COMT genotypes or haplotypes in cases and controls.
Conclusions: Our results suggest that the COMT -278A/G polymorphism may have a role in schizophrenia. The results are in agreement with recent findings in this field that indicate a minor influence of COMT G158A on schizophrenia risk and a greater importance of polymorphisms in the P2 promoter regions of COMT, such as -278A/G.