New Study Questions History of Childhood Trauma in Borderline Personality Disorder

Despite protestations in some quarters that it’s just a brain disorder and that’s all, almost all studies of subjects of borderline personality disorder (BPD) show a significant percentage of them were found to have a history of child abuse, including physical, sexual, and psychological. Since research subjects may not all be truthful about matters like that, the percentage is probably higher than those reported. Frank abuse is of not seen in all cases, of course. 

 

In getting to the bottom of the family dynamics of my psychotherapy patients over the last 40 year, I discovered that some of their parents are instead hyper-involved yet resentful helicopter parents who try to protect their children from any and all problems – which invalidates their children's ability to take care of anything on their own. Parents invalidating their kids’ thoughts and feelings, posited as one of the causes of the disorder by Marsha Linehan’s DBT – the predominant psychotherapy paradigm for the disorder – is an almost universal feature of BPD families.

 

A good meta-analysis (studies that combine the results of several study to add strength to the conclusions of any one study) that corroborates theoretical proposals that exposure to adverse life experiences is associated with BPD is “Childhood adversity and borderline personality disorder: a meta-analysis” by Porter et. al. in Acta Psychiatrica Scandinavia (2019).

 

A new study, however, seems to show that this is not the case (“Childhood trauma and borderline personality disorder traits: A discordant twin study” by Skaug, et al., Journal of Psychopathology and Clinical Science, (2019). But it has some of the same logical flaws I’ve documented in a previous post. It was a study of “discordant” twins (where one is healthier than the other) and was based on their self report using a structured interview called the Childhood Trauma Interview. Small but statistically significant associations between childhood trauma (CT) and BPD traits were initially found in the total sample. However, after controlling for “shared environmental” and genetic factors in the discordant twin pairs, the analyses showed little to no evidence for causal effects of CT on BPD traits. The authors concluded that the associations between CT and BPD traits stem from common genetic influences.

 

The elephant in the room here is the definition of “shared environment.” The assumption here is that both twins grew up in the same environment, which further presumes that their parents treated both of them the same. As anyone with a sibling or more than one child knows, this is nonsense. Differences in the way the parents treat the two children might even be exacerbated by the fact that one twin is healthier than the other, which could mean they had different parental responses to them at least some of the time. If you assume the shared environment is the same with parents treating both kids the same, of course genetic differences will stand out more. The study also ignores the fact that self reports about childhood abuse are often dishonest in order to go along with family rules about hiding such things from outsiders, so that its data in all likelihood also underestimates the prevalence of adverse childhood experiences, thereby minimizing any differences in the way each twin was treated.