THE PSYCHOBIOLOGICAL BASIS OF POSTTRAUMATIC-STRESS-DISORDER

Posttraumatic stress disorder is a disorder with an identifiable etiol ogical factor (exposure to a traumatic event) and with a complex sympt omatology (ie intrusive memories, avoidance, hyperarousal) that sugges ts dysfunction in multiple psychobiological systems. This review consi ders studies of the neurobiological consequences of acute and chronic stress showing that traumatic experiences can produce long-lasting alt erations in multiple neurochemical systems. The role of the locus coer uleus noradrenergic system, prefrontal cortex dopaminergic system, end ogenous opiates, hypothalamic-pituitary-adrenal axis, and cortico-rele asing factors are reviewed. Several models of PTSD are highlighted, in cluding fear conditioning, kindling, and sensitization. In particular, fear conditioning to explicit and contextual cues is proposed as a mo del for intrusive memories reactivated by trauma-related stimuli and h yperarousal, respectively. It is argued that the amygdala plays a cruc ial role in the encoding and retrieval of fear memories activated by s pecific stimuli that have been associated with aversive events, Associ ation involving more complex environmental stimuli and aversive events may require the involvement of the hippocampus and the bed nucleus of the stria terminalis. Repeated activation of conditioned fear memorie s may produce a kindling-like process which results in spontaneous int rusive memories.