According to researchers, "The highest linkage peak was found on chromosome 9p at marker D9S286 with a logarithm of odds score of 3.548 (empirical P=0.0001). "
Yeah, I don't know what that means either, but it implies that genetic origins continue to underscore mental illness as a real thing. So take that, nonbelievers!
For more, check out the Science Daily article here
Distel, M., Hottenga, J., Trull, T., & Boomsma, D. (2008). Chromosome 9: linkage for borderline personality disorder features Psychiatric Genetics, 18 (6), 302-307 DOI: 10.1097/YPG.0b013e3283118468