The incidence of BPD in patients with the 9,9, variant (five out of 19; 26.3%); or the 9,10 variant of the DAT1 gene (21 out of 106; 19.8%) was 2.36 times greater than the incidence of BPD in patients with the 10,10 variant (15 out of 179; 8.4%). This evidence concerns the gene SLC6A3 and Borderline personality disorder.