Leading candidate endophenotypes for SB include impulsive/aggressive personality traits, neuropsychological and neurophysiological responses, and functional changes in circuit activity as observed by brain imaging. Among these, only impulsive/aggressive personality traits meet all stringent endophenotype criteria. It is critical that future research efforts define the extent to which findings beyond impulsivity and aggression meet stringent endophenotype criteria including heritability, state independence and familial aggregation both in affected and unaffected relatives. Such putative endophenotypes may represent new and innovative outcomes that can be targeted to reduce the risk of SB, and future research efforts should be directed to defining the degree to which such traits are specific for SB and genetic in origin. Endophenotypes should help us to discover the pathophysiology-related mechanisms involved in SB, and lead to the identification of potential new biological systems as therapeutic targets.
