The enduring and contentious hypothesis that sleepwalking and night terrors: are symptomatic of a protective dissociative mechanism is examined. This is mobilised when intolerable impulses, feelings and memories escape, within sleep, the diminished control of mental defence mechanisms. They then erupt but in a limited motoric or affective form with restricted awareness and subsequent amnesia for the event. It has also been suggested that such processes are more likely when the patient has a history of major psychological trauma. In a group of 22 adult patients, referred to a tertiary sleep disorders service with possible sleepwalking/night terrors, diagnosis was confirmed both clinically and polysomnographically, and only six patients had a history of such trauma. More commonly these described sleepwalking/night terrors are associated with vivid dream-like experiences or behaviour related to flight from attack. Two such cases, suggestive of a dissociative process, are described in more detail. The results of this study are presented largely on account of the negative findings. Scores on the dissociation questionnaire (DIS-Q) were normal, although generally higher in the small " trauma " subgroup. These were similar to scores characterising individuals with posttraumatic stress disorder. This " trauma " group also scored particularly highly on the anxiety, phobic, and depression scales of the Crown-Crisp experiential index. Tn contrast the " no trauma " group scored more specifically highly on the anxiety scale, along with major trends to high depression and hysteria scale scores. Two cases are presented which illustrate exceptional occurrence of later onset of sleepwalking/night terrors with accompanying post-traumatic symptoms during wakefulness. It is concluded that a history of major psychological trauma exists in only a minority of adult patients presenting with sleepwalking/night terror syndrome. In this subgroup trauma appears to dictate the subsequent content of the attacks. However, the symptoms express themselves within the form of the sleepwalking/night terror syndrome rather than as rapid eye movement sleep related nightmares. The main group of subjects with the syndrome and with no history of major psychological trauma show no clinical or Df S-Q evidence of dissociation during wakefulness. The proposition that, within the character structure of this group, the mechanism still operates but exclusively within sleep remains a possibility.
