Context: Polymorphisms in the serotonin transporter gene (5-HTT) may influence antidepressant response to selective serotonin reuptake inhibitors (SSRIs). The norepinephrine transporter (NET) is the analogous target for norepinephrine reuptake inhibitors (NRIs).
Objective: To determine whether antidepressant responses to SSRIs or NRIs are associated with genetic polymorphisms of the corresponding monoamine transporters.
Design, setting, and patients: A 6-week naturalistic treatment study with blinded outcome evaluation of 241 Korean inpatients and outpatients with major depression at an academic psychiatry service. Patients were recruited to the study from March 1998 through February 2003.
Interventions: Treatment with an SSRI (fluoxetine or sertraline; n = 136) or an NRI (nortriptyline; n = 105) antidepressant. Adherence was assessed by measuring plasma concentration at 4 weeks. Patients were genotyped for s/l polymorphisms in 5-HTT promoter region (5-HTTLPR), 5-HTT intron 2 s/l variation, and NET G1287A variation of exon 9.
Main outcome measures: An SSRI and NRI response (defined as > or =50% decrease in Hamilton Rating Scale for Depression score at 6 weeks).
Results: NRI response was associated with the NET G1287A polymorphism (odds ratio [OR], 7.54; 95% confidence interval [CI], 2.53-22.49; P<.001). An SSRI response was associated with the 5-HTT intron 2 s/l variation (OR, 20.11; 95% CI, 4.27-94.74; P<.001). The 5-HTTLPR was also associated with an SSRI response (OR, 3.34; 95% CI, 1.41-7.91; P = .006). In contrast to studies in white patients, the favorable allele for SSRI response was S 5-HTTLPR. The S 5-HTTLPR was associated also with NRI response (OR, 3.73; 95% CI, 1.32-10.53; P = .01). The NET polymorphism was not associated with an SSRI response. The NET G1287A GG genotype (56% of the population) was associated with better response to the NRI (83.3% [35/42]) than to SSRI (58.7% [44/75]) (OR, 3.52; 95% CI, 1.39-8.95; P = .006). Some genotype combinations were associated with high rates of antidepressant response and others with low rates of response.
Conclusions: Monoamine transporter gene polymorphisms were associated with response to antidepressants with homologous monoamine transporter targets. Combinations of polymorphisms were informative for response and nonresponse. Confirmation of these preliminary findings would permit refined pharmacogenetic selection of antidepressant treatment.