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.

Table 1
Traumatic Amnesia Among Survivors of Physical Abuse, Rape, War, Accidents, and Disaster: Percent of Sample*
Source		Sample Size	Amnesia				Sample
			None	F +P	Partial	Full
Physical Abuse
	Elliott & Briere, 1995	485	75	25	15	10	general census
	Elliott & Fox, 1994	484	73	27	10	17	undergraduates
	Golding et al., 1996	613		21			undergraduates
	Melchert, 1996	553		21		11	college students
	Fish & Scott, 1999	423		21		10	counseling psychologists
	Femina et al., 1990	69	26/8†				9-year prospective
	Robins, 1966	524/71	78†				prospective study on delinquency
	Widom & Shepard, 1996	110		40			prospective study
Rape
	Elliott & Briere, 1995	485	77	23	10	13	general census
Combat
	Sargant & Slater, 1941	1000	85.6	14.4			WWII consecutive cases
	Elliott & Briere, 1995	485	61	39	23	16	combat
POW
	Wagenaar & Groeneweg, 1990	78	gist	Injury; death threat			Camp Erika
Car Accident
	Elliott & Briere, 1995	485	92	8	4	4	general census
Disaster
	Dollinger, 1985	33		3			child lightening victims
	McFarlane, 1988	469	100	57§			Australian bushfire
	Wilkinson, 1983	102	27‡				Hyatt skywalk collapse
	Eriksson & Lundin, 1996	53		29‡			m/s Estonia disaster
*  Adapted from Table 7.4 in Brown et al. (1998); F+P  = combined percentage of full and partial amnesia; † denial; ‡ memory disturbance (intrusive memory or amnesia);  § failed to report injury at 11 months

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.

Table 2
Amnesia for Childhood Sexual Abuse: Percent of Sample*
Source		N	F	P	F+P	No A		IC	Rx	c/nc	r/nr	Sample
Clinical Studies
	Herman & Schatzow, 1987	53	28	36	64	36		74	100	c	nr	Outpatient Rx
	Draijer, 1990	1,054			57							National survey
	Ensink, 1992	100	29	28	57	43			100	c	nr	Incest & rx groups (high DID)
	Albach et al., in press	97e 65c			35 1	65 99			100	c	nr	Women with hx of CSA Normal controls
	Cameron, 1994	60	42	23	65	35			100	c	nr	Women in rx with hx of CSA
	Loftus et al., 1994	105	19	12	31	69				c	nr	Women in drug tx
	Roe & Schwartz, 1996	52			77	23		44	68 32	c	nr	Women in inpatient tx
	Pomerantz, in progress	26	50	42.5	92.5	7.5				c	nr	Women in outpatient tx
	Gold et al., 1994	105	30	40	70	30				c	nr	Intake interview in rx
	Chu et al. 1999	74	34	26	60	41		89†	28			Female inpatients of a PTSD & dissociative disorders unit
Nonclinical Samples
	Bernet at el., 1993	624	36			64			30	nc	nr	College undergraduates
	Belicki et al., 1994	68			55	45				nc	nr	College undergraduates
	Kristiansen et al., 1995	113	25	26	51	49		61	93	nc	nr	Community sample, women
	Elliott & Fox, 1994	484	30	14	44	56			19	nc	nr	College undergraduates
	Van der Kolk & Fisler, 1995	36			42	58		75		nc	nr	Volunteers, terrible life experiences
	Roesler & Wind, 1994	228	28			72						Triggered by M. Van Derbur disclosure
	Grassian & Holtzen, 1996	42	19	28	47	53				nc	nr	Triggered by Father Porter disclosure
	Golding et al., 1996	613	13							nc	nr	College undergraduates
Random Samples
	Briere & Conte, 1993	450			59	41				c	r	In tx for CSA
	Feldman-Summers & Pope, 1994	330			40	60		47	56	nc	r	Psychologists
	Westerhof et al., in press	500	22	17	39	61		69	68	nc	r	Psychologists
	Fish & Scott, 1999	423	17	38	55	45			44	nc	r	Counselors
	Elliott & Briere, 1995	505	20	22	42	58			7 13	nc	nr	General population
	Polusny & Follette, 1996	223			30 39	70 61				nc	nr	Psychologists
	Melchert, 1996	553	18			82				nc	r	College undergraduates
	Golding, 1995	663	14							nc	r	Telephone survey
Prospective Studies
	Williams, 1994	129	38			62		100	0	nc	nr	Women with clinic documentation of CSA
	Widom & Morris, 1997	1,114	37			63		100		nc	nr	Court-substantiated CSA
	Burgess et al. 1995	22	14	27	41	59		100	0	c	nr	Daycare CSA
Other Studies
	Kluft, 1997	19	68			32		100	100	c	nr	DID pts in tx; confirmed abuse
	Goodman et al., 1995	1,652	4.5	45	50	50				c	nr	Ritual abuse allegations
Detailed Case Reports
	Duggal & Stroufe, 1998	1						100				Subject of a prospective & unrelated study
	Martinez-Taboaz, 1996	2						100				DID pts in tx; confirmed abuse
	Viederman, 1995	1						100				Woman in rx
* Adapted from Table 7.7 in Brown et al. (1998). † = Percentage of participants with full amnesia who attempted and obtained independent corroboration. KEY: N      = sample size F      = full amnesia/no memory for a significant period of time P      = partial amnesia F+P  = combined percentage of full and partial amnesia No A = no amnesia; continuous memory IC     = percentage of sample for which some sort of independent corroboration existed							Rx   = percentage of sample where memory recovery was associated with (but not necessarily caused by) therapy; percentage of sample where memory initially recovered in therapy c/nc = clinical vs. nonclinical sample r/nr =  random vs. nonrandom sampling rx     =   therapy Tx   =  treatment e      = experimental group c      = control group CSA =  childhood sexual abuse DID  = dissociative identity disorder

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.)

References

Albach, F., Moormann, P. & Bermond, B. (1996). Memory recovery of childhood sexual abuse. Dissociation, 9(4), 261-273.

Belicki, K., Correy, B., Boucock, A., Cuddy, M., & Dunlop, A. (1994). Reports of sexual abuse: Facts or fantasies? Unpublished manuscript. Brock University , St. Catherines , Ontario .

Bernet, C. Z., Deutscher, R., Ingram, R. E., & Litrownik, A. J. (November 1993). Differential factors in the repression of memories of childhood sexual abuse . Poster presented at the Annual Convention of the Association for the Advancement of the Behavioral Therapy, Atlanta , GA.

Briere, J., & Conte, J. (1993). Self-reported amnesia for abuse in adults molested as children. Journal of Traumatic Stress , 6 (1), 21-31.

Burgess, A. W., Hartman, C. R., & Baker, T. (1995). Memory presentations of childhood sexual abuse. Journal of Psychosocial Nursing, 33 (9), 9-16.

Cameron, C. (1994). Women survivors confronting their abusers: Issues, decisions, and outcomes. Journal of Child Sexual Abuse, 3(1), 7-35.

Chu , J., Frey, L., Ganzel, B., & Matthews, J. (1999). Memories of childhood abuse: Dissociation, amnesia, and corroboration. The American Journal of Psychiatry, 156, 749-55.

Dollinger, S. J. (1985). Lightening-strike disaster among children. British Journal of Medical Psychiatry, 58 , 375-383.

Draijer, N. (1990). Seksuell misbruik van door verwanten: Een landelijk onderzoek naar de omvang, de aard, de gezinsachtergronded, de emotionele etekeniss en de psychische en psychosomatische gevolgen [Sexual abuse of girls by relatives: A nation-wide survey of the nature, emotional signs and psychological and psychosomatic sequelae]. Den Haag: Ministerie van Sociale Zaken en Verkgelegenheid.

Duggal, S., & Sroufe, L. A. (1998). Recovered memory of childhood sexual trauma: A documented case from a longitudinal study. Journal of Trauma Stress, 11(2), 301-321

Elliott, D. M., & Briere, J. (1995). Posttraumatic stress associated with delayed recall of sexual abuse: A general population study. Journal of Traumatic Stress, 8(4), 629-47.

Elliott, D. M., & Fox, B. (1994). Child abuse and amnesia: Prevalence and triggers to memory recovery . Paper presented at the Annual Meeting of the International Society of Traumatic Stress Studies, Chicago, IL .

Ensink, B. J. (1992). Confusing realities: A study of child sexual abuse and psychiatric symptoms . Amsterdam: VU University Press.

Feldman-Summers, S., & Pope, K. S. (1994). The experience of "forgetting" childhood abuse: A national survey of psychologists. Journal of Consulting & Clinical Psychology, 62(3), 636-39.

Femina, D. D. , Yeager, C. A., & Lewis, D. O. (1990). Child abuse: Adolescent records vs. adult recall. Child Abuse & Neglect, 14(2), 227-31.

Fish, V., & Scott, C. (in press). Childhood abuse recollections in a non-clinical population: Forgetting, secrecy, dissociation, and absorption.

Gold, S. N, Hughes, D., & Hohnecker, L. (1994). Degrees of repression of sexual abuse memories. American Psychologist, 49, 441-442.

Golding, J. M., Sanchez, R., & Sego, S. A. (1996). Do you believe in repressed memories? Professional Psychology, Research and Practice, 27(5), 427-37.

Goodman, G. S., Qin, J., Bottoms, B. L., & Shaver, P. R. (1995). Characteristics and sources of allegations of ritualistic child abuse. Final report to the National Center on Child Abuse and Neglect.

Grassian, S., & Holtzen, D. (1996, July). Memory of sexual abuse by a parish priest . Paper presented at Trauma and Memory: An International Research Conference. Portsmouth , New Hamsphire.

Herman, J. L., & Schatzow, E. (1987). Recovery and verification of memories of childhood sexual trauma. Psychoanalytic Psychology , 4 (1), 1-14.

Kluft, R. P. (1997). The argument for the reality of the delayed recall of trauma. In P. S. Applebaum, L. A. Uyehara, & M. Elin (Eds.), Trauma and memory: Clinical and legal controversies (pp. 25-57). New York : Oxford University Press.

Kristiansen, C. M., Felton, K. A., Hovdestad, W. E., & Allard, C. B. (1995). The Ottawa survivor's study: A summary of the findings . Unpublished manuscript.

Loftus, E. F., Polonsky, S., & Fullilove, Mindy Thompson. (1994). Memories of childhood sexual abuse: Remembering and repressing. Psychology of Women Quarterly, 18(1), 67-84.

Martinez-Taboas, A. (1996). Repressed memories: Some clinical data contributing toward its elucidation. American Journal of Psychotherapy, 50(2), 217-30.

McFarlane, A. C. (1988). The longitudinal course of posttraumatic morbidity: The range of outcomes and their predictors. Journal of Nervous and Mental Disease, 176, 30-39.

Melchert, T. P. (1996). Childhood memory and a history of different forms of abuse. Professional Psychology, Research and Practice, 27(5), 438-46.

Polusny, M. A., & Follette, V. M. (1996). Remembering child sexual abuse: A national survey of psychologists' clinical practices, beliefs, and personal experiences. Professional Psychology: Research and Practice , 27(1), 41-52.

Pomerantz, J. (in progress). Memories of abuse: Women sexually traumatized in childhood . Unpublished manuscript, The Center for Trauma and Dissociation, Denver, CO.

Robins, L. N. (1966). Deviant children grown up: A sociological and psychiatric study of sociopathic personality. Baltimore , MD : Williams & Wilkins.

Roe, C. M., & Schwartz, M. F. (1996). Characteristics of previously forgotten memories of sexual abuse: A descriptive study. Journal of Psychiatry & Law, 24(2), 189-206.

Roesler, T. A.; & Wind, T. W. (1994). Telling the secret: Adult women describe their disclosures of incest. Journal of Interpersonal Violence, 9(3), 327-38.

Sargant, W., & Slater, E. (1941). Amnestic syndromes in war. Proceedings of the Royal Society of Medicine, 34, 757-764.

van der Kolk, B., & Fisler, R. (1995). Dissociation and the fragmentary nature of traumatic memories: Overview and exploratory study. Journal of Traumatic Stress , 8(4), 505-525.

Viederman, 1995

Wagenaar, W. A., & Groeneweg, J. (1990). The memory of concentration camp survivors. Applied Cognitive Psychology, 4, 77-87.

Westerhof, Y., Woertman, D., & Van der Hart, O. (in press). Forgetting childhood abuse: Feldman-Summers & Pope's (1994) study replicated among Dutch psychologists.

Widom, C. S., & Morris, S. (1997). Accuracy of adult recollections of childhood victimization: Part 2. Childhood sexual abuse. Psychological Assessment, 9(1), 34-46.

Widom, C. S., & Shepard, R. L. (1996). Accuracy of adult recollections of childhood victimization: Part 1. Childhood physical abuse. Psychological Assessment, 8(4), 412-21.

Wilkinson, C. B. (1983). Aftermath of a disaster: The collapse of the Hyatt Regency hotel skywalks. American Journal of Psychiatry, 140, 1134-1139.

Williams, L. M. (1994). Recall of childhood trauma: A prospective study of women's memories of child sexual abuse. Journal of Consulting and Clinical Psychology, 62 (6), 1167-76.