Background: Exposure to stressful life events increases the risk of developing a psychotic disorder. Moreover, increased reactivity to stress seems to represent part of the vulnerability for psychosis. This study aimed to investigate whether a functional polymorphism in the catechol-O-methyltransferase (COMT Val(158)Met) gene moderates the psychosis-inducing effects of stress.
Method: A semi-experimental stress exposure paradigm was used in a sample of 306 genotyped young men (aged 19-24 years), in whom measures of psychotic symptoms were obtained at recruitment in the Greek army (exposed condition) and again after 18 months of military training (unexposed condition).
Results: Stress exposure at army induction was associated with an increased level of psychotic symptoms. In addition, carriers of the COMT Val(158)Met Val allele were more susceptible to the effect of stress on the psychosis outcome than those with the Met/Met genotype (test for interaction: chi2 = 5.02, df = 1, p = 0.025).
Conclusion: The COMT Val(158)Met genotype may moderate the effect of stress on psychotic symptoms.