Here we demonstrated a significant association between the DRD4 -616 C/G promoter polymorphism and borderline traits in two independent samples. Low-income young adults as well as psychiatric patients carrying the CC genotype displayed more borderline symptoms. Moreover, the DRD4 promoter SNP combination of -616C ~ -521T showed association with BPD traits in both groups. Two DRD2 SNPs (TaqIA and TaqIB) were also associated with borderline traits among at-risk young adults, and the haplotype analyses confirmed the role of the DRD2 gene. However, neither of the DRD2 polymorphisms had any significant effect in the sample of psychiatric patients.
