In which situation should structural dissociation theory be applied? In which specific situation you think is most appropriate to apply Van der Hart's SDT?
According to a presentation given by Van Der Hart "Structural Dissociation of the
Personality: The Key to Understanding
Chronic Traumatization and Its
Treatment", this theory relates to the response to trauma, described further in the paper "Trauma-related dissociation: conceptual
clarity lost and found" (Hart et al. 2004).  From the abstract:


  It postulates a common psychobiological pathway for all
  trauma-related disorders. Trauma-related dissociation is maintained by integrative deficits
  and phobic avoidance. This conceptualization advances diagnosis, classification, treatment
  and research of trauma-related disorders.