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

INTRODUCTION AND OBJECTIVES: There 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.

METHODS: The 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).

RESULTS: No overall effect of genotype or genotypextime interaction was detected. However, we observed a genotypextime 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 (chi(2) = 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).

CONCLUSIONS: COMT 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.