The aim of the current dissertation is three-fold. First, we aimed to provide insight with regard to the alterations of traumatized youths’ neurobiological stress systems (PART I). We investigated sympathetic, parasympathetic, and HPA axis parameters among traumatized adolescents in residential care and a nontraumatized comparison sample. Both basal activity during rest and reactivity to acute social stress were evaluated. The outcomes of this study are described in Chapter 2.