Summary of Research Examining the Prevalence of Full or Partial Dissociative Amnesia for Traumatic Events
The most comprehensive review of the scientific literature on dissociative amnesia has been conducted by Brown, Scheflin and Hammond in their book, Memory, Trauma Treatment, and the Law . (New York: Norton, 1998). This book is viewed as setting the standard in the field after receiving the American Psychiatric Association's 1999 prestigious Manfred S. Guttmacher Award for best book in law and forensic psychiatry.
Brown, Scheflin and Hammond reviewed 43 studies relevant to the subject of traumatic memory and found that every study that examined the question of dissociative amnesia in traumatized populations demonstrated that a substantial minority partially or completely forget the traumatic event experienced, and later recover memories of the event.
Dissociative amnesia can occur after any type of traumatic event.
Research shows that a period of either partial or full amnesia is reported by between 30 and 90% of adult victims of childhood sexual abuse.
By 1999, over 68 studies had been published that document dissociative amnesia after childhood sexual abuse. In fact, no study that has looked for evidence of traumatic or dissociative amnesia after child sexual abuse has failed to find it. see: Brown, Scheflin, & Whitfield. (1999). Recovered Memories: The Current Weight of the Evidence in Science and in the Courts, Journal of Psychiatry & Law, 27, 5-156.
The reality of traumatic amnesia is further supported by investigations of memory and attention in carefully controlled laboratory settings.
For example, a study recently published in the prestigious journal Nature demonstrated that people have executive control processes that can prevent unwanted declarative memories from entering awareness. Anderson & Green, Suppressing Unwanted Memories by Executive Control, 410 Nature 366-369 (2001, March 15). See also Davis, Repression and the Inaccessibility of Affective Memories, 52 J. Personality & Soc. Psychol. 585-93 (1987). (Reviews laboratory research demonstrating that some individuals display limited accessibility to personal, real-life affective memories. The effect is particularly pronounced for experiences involving fear or embarrassment.)
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