I was reading an article called “Social cognition in borderline personality disorder: evidence for disturbed recognition of the emotions, thoughts, and intentions of others” and noticed a line in the article that said this: “Thus, in addition to high heritability of BPD (Torgersen et al., 2008), these results argue that environmental factors (e.g., trauma) contribute to disturbed social cognition in BPD. In summary, for the current study we expected PTSD to be a negative predictor of social cognition.” That intrigued me on two levels. One was the “high heritability” part, because often I see comments about BPD and how many people believe that it is mainly caused by childhood trauma (and/or invalidation). In WHINE I state this: As I said earlier, one of the causes of BPD is the “invalidating environment.” Now, it could be that it is not an actual “cause” (and that all the real causes of BPD are biological), but more a reinforcer of BPD. So, the second part of the article that intrigued me was the idea that “we expected PTSD to be a negative predictor of social cognition” – and the discussion and methodology of comorbid PTSD with BPD. What they found was that people with BPD (with or without comorbid PTSD) are less able to understand the intent, thoughts and motivations of social interactions in others – in other words, people with BPD can’t mentalize as well as controls. They also found that this lack of ability is more marked in people with BPD who also have comorbid PTSD. The fact that they mention comorbid PTSD at all is something of a revelation – or perhaps should be to us nons. Many people come to support lists and do research on the Internet and begin their “introduction” of their BPD person with a long list of childhood traumas that explains why the person has BPD. This current research would indicate that PTSD and BPD are clearly two separate disorders and that, while PTSD is a contributor to poorer functioning that BPD alone, BPD is in itself a highly inheritable disorder and biological in nature, yet “reinforced” or made more severe (especially in a social functioning sense) when PTSD is present.
Anyway, this research led me to another scientific study called “Familial Resemblance of Borderline Personality Disorder Features: Genetic or Cultural Transmission?” In which the researchers studied twins, siblings and parents of borderlines to determine the genetic underpinning of BPD or whether the environment and/or cultural influences could have more of an influence on the development of BPD. They found this: “In the present study an extended twin-family design was applied to self-report data of twins (N = 5,017) and their siblings (N = 1,266), parents (N = 3,064) and spouses (N = 939) from 4,015 families, to estimate the effects of additive and non-additive genetic and environmental factors, cultural transmission and non-random mating on individual differences in borderline personality features. Results showed that resemblance among biological relatives could completely be attributed to genetic effects.” and this: “There was no effect of cultural transmission from parents to offspring.”
Recently, in the ATSTP group, we have been discussing the idea that shame/honor-based cultures and whether that environment could be explanatory in some sense of the development of BPD. It appears (at least based on this 2009 study) that the development and transmission of BPD is NOT cultural. It is essentially genetic (mainly “additive”, meaning it is more than one gene involved) and the environment has an effect, yet cultural transmission was not apparent.
They do go on to say this: “Gene by environment interaction implies that genes determine the degree to which an individual is sensitive to an environment. In the presence of gene-environment interaction, individuals with a ‘sensitive’ genotype will be at greater risk of developing BPD if an undesirable environment is present, than individuals with an ‘insensitive’ genotype.” So, basically, although this interaction has not been fully studied, it appears that some sort of “sensitive” genotype is required to develop BPD.