The data analysis showed that there was a significant difference in the frequencies of 5-HTTLPR genotypes (SS, SL, LL) between the experimental and control groups (t1). In particular, the homozygosity of short alleles was significantly associated with poststroke major depression. Since S-allele may have dominant negative effect on basal transcriptional activity,6 we combined SS and SL into one group and compared with LL between depressed and nondepressed stroke patients. The results remained statistically significant (χ2=6.04, df=1, p=0.025). Furthermore, the depressed group had significantly higher rate of personal history of MDD and or anxiety disorder and family history of MDD and or bipolar disorder than the nondepressed group. There were no differences between case and control groups in age, gender, laterality of lesions, Barthel measures, MMSE scores, sum of vascular diseases and medications, and time since stroke. There were no differences in genotype frequencies between stroke subjects with and without personal history (χ2= 1.33, df=2, p=0.51) and family history (χ2= 2.59, df=4, p=0.63). Due to small sample size, we performed two logistic regression analyses separately for personal and family history in order to examine the independent effect of genotypes on depression. The regression of genotype and personal history on depression diagnosis yielded no significant effect of genotype (Wald χ2=5.63, df=2, p=0.06). Similarly regression of genotype and family history on depression failed to show any significant effect of genotype (Wald χ2=3.08, df=2, p=0.22). In an attempt to account for the higher frequency of women in the depressed group (46.2%) than in the nondepressed group (24%), we examined the effect of gender on genotypic frequencies and on the association between poststroke major depression and genotypes. There were no gender differences in genotypic frequencies (χ2= 3.65, df=2, p=0.16). The effect of genotype on depression remained significant even after controlling for gender (Wald χ2= 7.2649, df=2, p=0.027).