Analysis of COMT gene (Val 158 Met polymorphism) in the clinical response to SSRIs in depressive patients of European origin

Introduction and objectivesThere is convincing evidence of interactions between serotonergic and dopaminergic systems and it seems that an increase of dopamine concentration in the whole brain could be a limiting factor for the antidepressant like effect of antidepressants. The COMT gene might be a good candidate for explaining some aspects of the pharmacological response to SSRIs.MethodsThe aim of our study was to analyse the Val 158 Met functional polymorphism on COMT gene and clinical response (4 weeks) and clinical remission (6/8 and 12 weeks) in two samples of depressive patients (DSM-IV) treated with SSRIs of Italian and Spanish origin. Clinical outcome was measured using 21 items Hamilton scale, weekly in the Italian sample (along 6 weeks) and monthly in the Spanish one (along 12 weeks).ResultsNo overall effect of genotype or genotype × time interaction was detected. However, we observed a genotype × time interaction on HDRS decrease for citalopram treatment (F(4.6,317.5) = 3.38, P = 0.007) in the Spanish sample. No clear effect was observed in the Italian sample. The three samples were pooled in order to test if carrying the Met/Met genotype confers an increased risk for non-remission at 6–8 weeks. The results showed that Met/Met carriers have an odds ratio of 2.21 (95% CI [1.20–4.12]) for non-remission (χ2 = 7.43, df = 2, P = 0.006). The Met/Met effect was not observed in response at 4th week (for all SSRI treatments) or in remission at 12th week (citalopram treatment).ConclusionsCOMT gene could have a small and indirect effect of clinical response to SSRIs by slowing-down the antidepressant action along the follow-up, basically in citalopram treatment.