['Ethnic differences in genotype frequency provide a natural condition for assessing the contribution of gene variations to the causes and treatments of disease. Accordingly, the purpose of this study was to determine whether ethnic variations in allele frequencies of the serotonin transporter gene-linked polymorphic region (5-HTTLPR) of the SLC6A4 gene were related to the response to the treatment of depression.', 'African-Americans (n=101) and Caucasians (n=100) with major depressive disorder were treated with the antidepressant citalopram (20-60mg/day) for 8weeks. Genotyping for the long (L) and short (s) alleles (LL, Ls, and ss) of the SLC6A4 gene was performed and the association between genotype and treatment response was assessed.', 'Subjects in both ethnic groups showed a significant reduction in depression scores over time (p<.0001). However, in spite of a significantly greater frequency of the L allele in African-Americans as compared to Caucasians, a comparable clinical response between the two groups was found with 5-HTTLPR polymorphism not significantly associated with clinical response in either ethnic group.'] Is response to citalopram associated with SLC6A4 genotype in African-Americans and Caucasians with major depression?