When Kardiner first described the full syndrome of what is now called PTSD in 1941, he called the trauma response a “physioneurosis,” that is, a mental disorder which affects both the soma and the psyche. Now, more than 40 years later much knowledge has been gained about the biological effects of traumatization. Based on the studies of disruptions of attachment bonds in non‐human primates, the animal model of inescapable shock, and numerous studies of traumatized children and adults, we are beginning to understand the nature of the biological changes which underlie the psychological response to trauma. This paper will explore (1) the nature of the biological alterations in response to traumatization, (2) how these biological shifts depend on the maturation of the central nervous system (CNS), cognitive processes, and the social matrix in which they occur, (3) and how these alterations can influence psychopathological and interpersonal processes.