Since impulsive self-damaging behaviors constitute one of the core features of BPD, our DRD2 findings might support the association between the DRD2/ANKK1 A1-allele and impulsive behavior reported in healthy young adults [25,26]. Checking for the most frequent symptoms in the studied groups indicated that US young adults displaying two or more borderline symptoms were indeed more likely to exhibit the two forms of impulsivity, namely criterion 4 (impulsive self-damaging behaviors, 75%) and criterion 5 (suicidal or self-mutilating behavior, 50%). Another frequent symptom in this group was intense and unstable relationships (55%). Interestingly, the DRD2 genetic association results can also be related to this phenotype, since pair bonding in monogamous rodents is partially linked to D2 receptors in nucleus accumbens and to the mesolimbic dopamine reward system [52]. Moreover, the A1-allele has been associated with pair-bonding behaviors in humans, as individuals with this low-expression DRD2 allele were less likely to want to marry or have children [28]. This observation is in agreement with animal studies where administration of a DRD2 antagonist inhibited pair bond formation [reviewed in [53]].
