On the other hand, depressive patients with borderline features displayed more symptoms from the emotional disturbance domain (chronic feelings of emptiness: 72.1%, affective instability: 67.6%, intense anger: 67.6%). Also, paranoid ideation or dissociative symptoms were quite frequent (68.4%) in this group. Based on the differences in BPD symptoms and in the genetic association findings, we hypothesize that the DRD4 genetic association (present in both samples) might indicate a dopaminergic vulnerability to BPD symptom development involving the D4 dopamine receptor expressed preferentially in the prefrontal cortex. Whereas the DRD2 genetic findings (present only among young adults) are related more to the impulsive phenotype and/or to less effective pair bonding, with an altered striatal D2 dopamine receptor neurotransmission in the background. The nominally significant effects of DRD2 polymorphisms on substance abuse in our sample might also relate to the association between DRD2 and impulsive self-damaging behaviors.
