SLC6A3 and post-traumatic stress disorder: Furthermore, the presence of A1+ allele (A1A2, A1A1 genotypes) of dopamine D2 receptor genes has been associated with a higher incidence of PTSD [27] and Segman [28] has found an association of the allele 9 of the dopamine transporter gene (DAT1) polymorphism and the development of PTSD.