Violence in schizophrenia: An association with comt genotype

Two studies have reported associations between the low activity polymorphism of the catechol-O methyltransferase (COMT) gene and violence in schizophrenia (1,2). We recruited 180 individuals (UK ethnicity) with DSM-IV schizophrenia. Violent episodes were rated from interview and case-note review, and a rating of violence obtained using the Overt Aggression Scale (OAS) (3). COMT polymorphism was determined by RFLP analysis. A significant association was found between COMT genotype and OAS score (p=0.0157), with the only significant difference between the genotypes being between the high activity homozygote and the heterozygote (p = 0.025). The odds ratio for severe violence comparing the high activity homozygote with the other genotypes was 2.07, with a 95% confidence interval of (1.03, 4.15). An association was also found between gender and OAS score (p = 0.015), with males having a higher mean score than females. There was no significant difference in the distribution of genotypes across gender or in the duration of illness compared across genotypes or gender. Our results contradict findings from the two previous studies. The larger sample in our study makes a Type II error unlikely, and highlights the need for further research in this field.