Association analysis of SCN9A gene variants with borderline personality disorder

Borderline personality disorder (BPD) is a serious psychiatric disorder affecting about 1-2% of the general population. Key features of BPD are emotional instability, strong impulsivity, repeated self-injurious behavior (SIB) and dissociation. In the etiology of BPD and its predominant symptoms, genetic factors have been suggested. The voltage-gated sodium channel Nav1.7 is expressed in sensory neurons and in the hippocampus, a key region of the limbic system probably dysfunctional in BPD and dissociative disorders. The alpha-subunit of Nav1.7 is encoded by the SCN9A gene on chromosome 2 and variations of SCN9A can lead to complete inability to sense pain. The aim of the present study was to test for associations between SCN9A gene variants and BPD as well as BPD-related phenotypes. We genotyped ten tagging single nucleotide polymorphisms (SNPs) within the SCN9A gene in 161 well-defined Caucasian BPD patients and 156 healthy controls. We found no globally significant association of SCN9A markers with BPD at level 5%. However, in the female and in the male subsample, different SCN9A markers and individual haplotypes showed uncorrected p-values<0.05. In addition, p-values<0.05 were observed in the analysis of associations between SCN9A markers and dissociative symptoms. Although our results were largely negative, replication studies in an independent sample are warranted to follow up on the potential role of SCN9A gene variants in BPD and dissociative symptoms, paying special attention to a possible gender different etiology.