Borderline personality disorder (BPD) was first described 75 years ago (Stern, 1938), but only became accepted in the classification of mental disorders decades later (American Psychiatric Association, 1980); but it was at that point that research on the disorder took off. Formal investigation of BPD also led to a reformulation of its nature, moving from a condition lying on a “border” between neurosis and psychosis to a personality disorder rooted in underlying traits but associated with prominent symptoms. Thus BPD emerges from complex and interactive biological and psychosocial risk factors (Crowell, Beauchaine, & Linehan, 2009; Paris, 2007). There is no single explanation for its cause, and risks are not the same in all patients. The pathways to BPD demonstrate equifinality, with different pathways capable of leading to the same outcome (Cicchetti & Rogosch, 2002).