DRD4 and Borderline personality disorder: The estimated haplotype analyses for the DRD4 -616 C and -521 T alleles showed association with BPD traits in both samples: US young adult sample: likelihood ratio χ2 = 10.41, df = 3, p = 0.015; Hungarian patient sample: likelihood ratio χ2 = 9.81, df = 3, p = 0.02.