Biological Mechanisms in Posttraumatic Stress Disorder Relevance for Substance Abuse

Chronic post traumatic stress has been described as a "physioneurosis" (Kardiner 1941), that is, a mental disorder with both psychological and physiological components. The behavioral sequelae of inescapable shock in animals and of massive psychic trauma in people show a striking parallel. Inescapable shock in animals leads to both transient catecholamine depletion and subsequent stress-induced analgesia. We postulate that the numbing and catatenoid reactions following trauma in humans correspond to the central nervous system (CNS) catecholamine depletion that follows inescapable shock in animals. We further explore the evidence for a human equivalent of "stress-induced analgesia" in animals, which is known to be mediated by endogenous opioids. Although reexposure to trauma may produce a paradoxical sense of calm and control due to endogenous opioid release, a cessation of traumtic stimulation will be followed by symptoms of opioid withdrawal and physiological hyperreactivity mediated by CNS noradrenergic hypersensitivity. This hyperreactivity can, in turn, be temporarily modified by reexposure to trauma. This factor could account for voluntary reexposure to trauma in many traumatized individuals and would provide a complementary formulation to the conventional psychodynamic concept of attempted mastery of the psychosocial meaning of the trauma.