It is known from twin studies that genetic susceptibility factors, independent of an additional psychiatric diagnosis, modify the risk of SB.6, 24, 25 Therefore, it is probable that genetically delineated endophenotypes exist that are associated with such behaviors.14, 26 Although there are many potential endophenotypes that are associated with SB,27 we selectively provide a brief review of some associations (Figure 1). As reviewed previously, additional putative endophenotypes may be considered for further researches.14 Specific psychiatric disorder subtypes (for example, early onset major depressive disorder) and personality dimensions or disorders (for example, borderline personality disorder) have also been linked to SB.14 Few of the reported alterations fulfill the complete definition of an ideal endophenotype. As such, a majority of the studies reported below should be seen as promising, but not yet definitive, areas of research.
