Amygdala and hippocampal volume reductions as candidate endophenotypes for borderline personality disorder: A meta-analysis of magnetic resonance imaging studies

Borderline personality disorder (BPD) is a genetically influenced psychiatric illness with disruptions in neural systems supporting cognition and emotion regulation. Volumetric decreases of the hippocampus and amygdala may characterize BPD and serve as putative endophenotypes for the illness. The purpose of the present study was to evaluate whether the magnitude of these volume reductions and their associations with state-of-illness factors and psychiatric disorders which often co-occur with BPD warrant their consideration as potential endophenotypes. Volumetric magnetic resonance imaging results from 11 studies comprising 205 BPD patients and 222 healthy controls were quantitatively synthesized using meta-analytic techniques. Patients showed an average 11% and 13% decrease in the size of the hippocampus and amygdala, respectively. These volumetric differences were not attenuated in patients being treated with psychotropic medications. Comorbid depression, post-traumatic stress disorder, and substance use disorders were unrelated to volumetric decreases in either structure. These findings suggest modest volume reductions of the amygdala and hippocampus bilaterally in BPD which cannot be attributed to illness state or comorbid psychopathology. Decreased volumes of these key limbic structures may hold promise as candidate endophenotypes for BPD.