Aggressive behaviour in patients with schizophrenia is associated with catechol-O-methyltransferase genotype

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Abstract
Background: Evidence exists for an association between aggression and schizophrenia. Although the aetiology of aggression is multifactorial, three studies have reported associations between polymorphisms of the catechol-O-methyltransferase (COMT) gene and aggression in schizophrenia.Aims: To replicate these findings in a larger sample using the Overt Aggression Scale (OAS).Method: A sample of 180 people with DSM–IV schizophrenia were rated for aggression using the OAS. Kruskal–Wallis and contingency table analyses were applied to the OAS results.Results: The high-activity homozygotes showed significantly higher scores of aggression, whereas the heterozygotes showed significantly lower scores. The odds ratio for aggression for the high-activity homozygotes was 2.07 (95% Cl=1.03–4.15), whereas that for the heterozygotes was 0.54 (95% CI=0. 30–1.00).Conclusions: The high-activity COMT homozygote confers a higher risk of recorded aggression in schizophrenia. Heterozygotes had a significantly lower risk, which may represent an example of heterosis/heterozygote advantage.