(Click here  for more coverage of Borderline Personality Disorder.)
DSM-IV  (the “Diagnostics and Statistics Manual, 4th edition” — a reference book for those working in mental health care) estimates the prevalence of BPD  is 2%, meaning that 2 out of every 100 people suffer from the disorder. However, DSM-IV was published in 1994, a long time ago. Since then, considerable research has shown the 2% rate may be a significant underestimate.
A telephone study in Iowa in the 1990s indicated that possibly 7% of the population suffers from BPD .
In April 2008, a study was published in the Journal of Clinical Psychiatry  that involved 34,653 adults with men and women equally represented. The participants were extensively interviewed in 2004 to 2005. This study concluded that the prevalence of BPD  is 5.9%, about three times that of the DSM-IV estimates.
The study also shows that the oft-repeated 3:1 female-to-male ratio of BPD sufferers (i.e., 75% are female) may not be accurate. The study found that the number of women sufferers was only slightly higher than for males.
Additionally, high rates of concurrent additional mental health disorders were identified with mood disorders  and anxiety disorders . In particular, strong associations with bipolar disorder , schizotypal personality disorder , and narcissistic personality disorder  were noted.