According to Timothy Trull, Ph.D., professor of psychology at the University of Missouri College of Arts and Science, there is strong evidence that the answer to both of these questions is yes.
“There is good evidence that we find increased rates of borderline pathology in the relatives of target individuals that have BPD than when you compare them to people whose relatives don’t have BPD,” Trull said during a recent NEA-BPD call-in lecture.
Because there are 258 ways one can meet the diagnostic criteria of Borderline Personality Disorder, Trull said, the disorder may appear to be heterogeneous.
“The good news is that we’re finding that one general underlying dimension describes the relationships amongst the symptoms pretty well,” he said. “That’s good for genetic-type research because the first thing in genetic studies is to have a well-defined phenotype.”
Does BPD Run in Families?
Studies show increased incidences of Borderline Personality Disorder in people who have relatives — usually first-degree relatives — who also suffer from the disorder. This is most often a parent with Borderline Personality Disorder.
“We get estimates that anywhere from 9 percent to 25 percent of those with relatives diagnosed with Borderline Personality Disorder would experience some sort of borderline pathology,” Trull said, “the range depending on the severity of the diagnosis, inpatient versus outpatient cases, etc.”
So it would seem, he suggests, that both Borderline Personality Disorder itself, as well as the traits of BPD, seem to run in families.
Studies on Genetics and BPD
In talking about different ways this connection has been studied, Trull suggested that studies in adoptive families would be helpful in monitoring this connection. But there are none.
“In adoption studies you’d take advantage of something that happens by chance,” he suggested. “A kid with a biological parent (usually a mother, as that would be easier to track) with Borderline Personality Disorder is, for whatever reason, given up around birth for adoption and placed in a foster home.
“If you tracked those kids versus kids who had biological moms without BPD, you could look at rates of BPD to the extent that you’d potentially find higher rates of Borderline Personality Disorder with kids who had moms with BPD, though you don’t have the environmental influence of that biological mother.”
Although adoption studies in Borderline Personality Disorder research do not yet exist, there are ongoing twin studies. These are valuable in the fact that identical twins share almost 100 percent of their genetic make-up.
Tracking the occurrence of Borderline Personality Disorder in two people with, practically speaking, the same genetic make-up and a shared environment is important in the genetic study of BPD. Still, Trull takes into account the element of unique environmental effects.
“These are unique effects. Not experiences shared by the family, but experiences that happened to an individual outside the context of the family,” Trull said. “For instance, an experience of trauma, rape, or even deviant peers.”