In this chapter, we reviewed a hyperbolic model in which the core characteristic of BPD involves maladaptive emotional responses to an interaction between kindling events and hyperbolic temperament (i.e., emotional hypochondriasis). We also extended this model empirically in three ways. First, we showed that the interaction between emotional hyperbole and kindling events specifically indicates borderline psychopathology. Second, we showed that hyperbolic temperament is most strongly related to the stable, temperamental aspects of BPD involving internal dysphoria and interpersonal dependency that are responsible for ongoing psychosocial impairment and less related to the acute aspects of BPD involving impulsive behaviors and interpersonal patterns, such as entitlement and manipulation that tend to be the initial focus of treatment. Third, we identified key markers of hyperbolic temperament and how they are associated with BPD relative to depression. In particular, we showed that the association between BPD and MDD can be largely explained by a vulnerability to negative moods, whereas the difference between these disorders involves emotional reactivity to stressful interpersonal situations.

We have argued that the hyperbolic model provides an integrative framework for differentiating BPD from depression and other mood problems. This framework clarifies some central conceptual problems in the diagnosis of BPD and provides a useful model for differential diagnosis in applied settings. However, our knowledge about hyperbolic temperament as a construct remains limited, raising a number of theoretical challenges as well as directions for future research. For example, although studies exist on the stability of BPD [80–88], there is little research on the stability of hyperbolic temperament. Similarly, evidence about how hyperbolic temperament and kindling events interact with each other over time is limited. Finally, methods for addressing aspects of hyperbolic temperament clinically remain to be developed and tested. Nevertheless, the hyperbolic model provides a promising conceptualization of BPD that can inform differential diagnosis, frame treatment, and offer insights or directions for future research.