Borderline personality disorder (BPD) is a severe mental disorder with a high mortality rate as a result of suicide and impulsive behavior [1]. The core symptoms include emotional disturbance (affective instability, intense anger, chronic feelings of emptiness), disturbed cognition (identity disturbance, transient paranoid ideation or dissociative symptoms), impulsivity (suicidal or self-mutilating behavior, or other self-damaging behaviors, such as substance abuse, reckless driving, unsafe sex, spending sprees, binge eating), and interpersonal problems (intense unstable relationships, fear of abandonment). Interaction of multiple genetic factors and distressing childhood experiences has been suggested in the development of emotional dysregulation and impulsivity, leading to BPD symptoms [1]. The first family studies indicated substantial genetic underpinnings [2], and twin studies showed 42-69% heritability estimates [3,4]. Animal and human studies have indicated that reduced serotonin function and increased norepinephrine activity in the brain lead to aggressive and impulsive behavior [5]. Although several impulsive behaviors (e.g. ADHD: Attention Deficit Hyperactivity Disorder or substance abuse) have been linked to altered dopamine function, involvement of the dopamine system in BPD has been circumstantial. The main supporting evidence, thus far, comes from the therapeutic effect of D2 receptor blocking antipsychotic drugs [6].
