5-HT2A gene variants influence specific and different aspects of antidepressant response in Japanese and Italian mood disorder patients

The 5-HT2A receptor is a key modulator of the serotonin pathway. We previously observed a marginal association between 5-HT2A gene variants and antidepressant efficacy in Japanese and Italian population but in the opposite direction. In the present report, we hypothesize that discrepant findings on 5-HT2A gene variants could be due to both the effect of ethnicity and a possible specific effect on some symptom improvement. The sample comprised 203 patients affected by mood disorders and treated for major depression with paroxetine or fluvoxamine. The total depressive scores for all patients were analyzed in previous reports, but symptomatologic clusters were not examined previously. The 21-item Hamilton Rating Scale for Depression (HAM-D) was administered to evaluate depressive symptoms at baseline and bi-weekly over 6 weeks of treatment. All patients were genotyped for the 5-HT2A T102C polymorphism. Compared with patients with the 5-HT2A T and C variants, in the Japanese sample T allele carriers showed selective and slower score reductions than C allele carriers in delusion and activity symptoms; on the other hand, in the Italian sample, C allele carriers showed a slower and selective score reduction compared with T allele carriers in Somatic anxiety, while they did not differ from other patients on the other scores. Despite the limitations of the small sample size and modest significance levels, these findings suggest that response to SSRIs is not a unitary phenomenon and discrepant findings across ethnic groups may be due to differential effects of gene variants.