White et al: Results from a twin study based on structural interviews in a clinical sample suggest that heritability is estimated to be 69% Borderline, 63% Histrionic, and 77% Narcissistic personality disorder.

In a more recent study by Torgersen et al:

• Conducted a population-based twin study. Heritability was estimated to be 38% for anti-social personality disorder, 31% for histrionic personality disorder, 24% for narcissistic personality disorder, and 35% for borderline personality disorder. There were no shared environmental influences or sex differences were found.