Article read: Gunderson et al., 2011

Title: Family Study of Borderline Personality Disorder and Its Sectors of Psychopathology

This article on borderline personality disorder (BPD) had 2 purposes: First, to see if there was some kind of heritability for the disorder, and secondly to evaluate different models for the definition of the disorder.

Prior work had shown that there was heritability, but there were problems with the studies and the body of work on the subject is less well-developed than for some other disorders. The authors did find that there was heritability. If you have an immediate relative with BPD, there is a 3 to 4 times higher chance of also having BPD. The base level of BPD occurrence in this study was 4.9%, and other estimates range from 2% to 6%. Most (not all) diagnosed patients of BPD are women, so all the initial subjects (probands) in this study were women.

For the evaluation of different models, they were looking at 3 of them. One is where there is this one disorder, which they term "BPD-ness", and it manifests in 4 different areas sectors. The sectors are Affective, Interpersonal, Behavioral, and Cognitive and are consistent across models. The next model has the four different areas having common genetic and environmental factors causing them. The third model basically has little relation between the four areas, and is a non-theoretical mathematical baseline, a Cholesky model.

What are the different sectors?
Affective is dealing with feelings. For this disorder it's things like depression, anger, and unstable moods.

Interpersonal is dealing with relationships. Here the main things are intense relationships with lots of drama and fear of abandonment.

Behavioral is dealing with actions. Self-harm is the big one here, but other impulsive behaviour is also implicated.

Cognitive is dealing with thoughts. Weird thoughts, dissociation, paranoia are all possible symptoms in this sector.

Using statistics, including the AIC and BIC I described in a previous post, the authors found that both the theoretical models are superior fits to the data than the mathematical decomposition model. This is good. We do have a clue, at least a little bit. The AIC was only slightly able to distinguish the two models, but agreed with the BIC which gave a strong indication that the one disorder of "BPD-ness" underlies all the diagnosis sectors instead of them being independent results.

On to results: BPD has an underlying disorder of which the different sectors are manifestations. It has a heritable, probably genetic component of about 50%, but no specific genes have been identified. These results support those found in other studies of BPD, heritability, and model.

There are some caveats, of which I find most important is the following: Not all possible sectors associated with BPD were assessed. Including other sectors could change the model significantly.
Of course, any unknown bias in the sample selection could mess things up too.

Source:
Gunderson et al. Family Study of Borderline Personality Disorder and Its Sectors of Psychopathology. Arch Gen Psychiat (2011) vol. 68 (7) pp. 753-762