Dissociative Identity Disorder: Overview and Current Research
Research and Conclusions
Research trends currently focus on neurobiological and psychobiological factors unique to this disorder. For example, one study investigated the differences between alters who have access to traumatic memories and alters who suppress such information. The results indicate that different alters demonstrate differences in emotional, sensori-motor, cardiovascular, and regional cerebral blood flow in response to traumatic memories (Reinders, et al., 2006).
Another study sought to apply known findings about related disorders to DID. Because individuals diagnosed with disorders involving an etiology of stress (e.g., Post-Traumatic Sstress Disorder, Borderline Personality Disorder, Major Depressive Disorder with childhood trauma) have demonstrated a reduction in hippocampal volume, the authors of this study used magnetic resonance imaging and volumetric analyses to determine if any relationship also existed between DID and reduced hippocampal volume. Results indicated that the volume of the hippocampus of participants with DID was 19.2% smaller and the amygdala was 31.6% smaller than normal controls (Vermetten, Schmahl, Lindner, Loewenstein, & Bremner, 2006).
Other studies have discovered findings that are relevant to the relationship between trauma and memory in DID. A case study investigating the neural correlates of switching between alters used functional magnetic resonance imaging to study changes in the brain during switching. The results indicated that during switching to the alternate personality, the client’s bilateral hippocampus was inhibited, as well as the right parahippocampal gyrus, right medial temporal lobe, globus pallidus, and substantia nigra. However, during transition to the host personality, the right hippocampus demonstrated evidence of increased activation, with no inhibition in any brain structures (Tsai, Condi, Wu, & Chang, 1999). These findings contribute to an understanding of amnesia between alters, since regions of the brain involved in memory are either inhibited or activated.
Other research supports the idea that alters develop to protect the host from unpleasant thoughts and memories involving trauma and abuse. Autobiographical memories may differ between alter personalities, allowing the host to retain positive memories while alters contain negative traumatic memories (Bryant, 2005). A study investigating directed forgetting found that “dissociative patients showed directed forgetting between states, but not within the same identity state” (p. 241). This study clarifies the mechanism and function of memory in various dissociative states and helps explain why trauma might result in the development of alters. Pushing threatening material out of consciousness can then be facilitated by a switch from one state of consciousness to another (Elzinga, Phaf, Ardon, & van Dyck, 2003).
While clinicians now understand more about DID than in the past, additional research is needed to clarify and further investigate the nature of DID. The research that has been completed on this disorder still leaves many questions unanswered. For example, future research should further examine risk factors, and clarify how genetic and environmental factors contribute to this disorder. More studies should determine the nature of the physical and psychological differences evident among alters, how they develop, and their significance. Psychopharmacological studies are needed to determine which medications work best, and why they are effective.
Multicultural research is necessary to determine how sociocultural factors affect the development and clinical presentation of DID. Additional research in this area will not only benefit individuals with DID and their families, but also the research and clinical psychology community as a whole. Gaining an improved understanding of Dissociative Identity Disorder involves more than the categorization of another mental disorder. Increased knowledge in this area also contributes to an improved understanding of the nature of consciousness and the mind-brain relationship, as well.
American Psychiatric Association. (2000). Diagnostic and statistical manual of mental disorders (text revision). Washington, DC: Author.
Ballew, L., Morgan, Y., & Lippmann, S. (2003). Intravenous diazepam for dissociative disorder: Memory lost and found. Psychosomatics, 44, 346-347.
Becker-Blease,K., Deater-Deckard, K., Thalia Eley, E., Freyd, J., Stevenson, J., & Plomin, R. (2004). A genetic analysis of individual differences in dissociative behaviors in childhood and adolescence. Journal of Child Psychology and Psychiatry 45(3), 522–532.
Brand, R., Classen, C., Lanius, R., Loewenstein, R., McNary, S., Pain, C., & Putnam, F. (2009). A naturalistic study of Dissociative Identity Disorder and Dissociative Disorder NotOtherwise Specified patients treated by community clinicians.Psychological Trauma: Theory, Research, Practice, and Policy, 1(2)153–171.
Bryant, R. (2005). Autobiographical memories across personalities in Dissociative Identity Disorder: A case report. Journal of Abnormal Psychology, 104(4), 625-631.
Buchele, B. (1993). Group psychotherapy for persons with multiple personality and dissociative disorders. Bulletin of the Menninger Clinic, 57(3), 362.
Cormier, J., & Thelen, M. (1998). Professional skepticism of Multiple Personality Disorder. Professional Psychology: Research and Practice 29(2), 163-167.
Elzinga, B., Phaf, R., Ardon, A., & van Dyck, R. (2003). Directed forgetting between, but not within, dissociative personality states. Journal of Abnormal Psychology, 112(2), 237–243.
Fujii, Y., Suzuki, K., Sato, T., Muraka, Y., & Takahashi, T. (1998). Multiple Personality Disorder in Japan. Psychiatry and Clinical Neurosciences, 52, 299-302.
Gleaves, D., May, M., & Cardena, E. (2001). An examination of the diagnostic validity of dissociative identity disorder. Clinical Psychological Review, 21(4), 577-608.
International Society for the Study of Dissociation. (2005). [Chu, J., Loewenstein, R., Dell, P., Barach, P., Somer, E., Kluft, R., Gelinas, D., Van der Hart, O., Dalenberg, C., Nijenhuis, E., Bowman, E., Boon, S., Goodwin, J., Jacobson, M., Ross, C., Sar, V., Fine, C., Frankel, A., Coons, P., Courtois, C., Gold, S., & Howell, E.]. Guidelines for treating Dissociative Identity Disorder in adults. Journal of Trauma & Dissociation, 6(4) pp. 69-149.
Kaplan, B., & Sadock, V. (2008). Kaplan and Sadock’s concise textbook of clinical psychiatry. Philadelphia, PA: Lippincott Williams & Wilkins.
Korol, S. (2008). Familial and Social Support as Protective Factors Against the Development of Dissociative Identity Disorder [Abstract].Journal of Trauma & Dissociation, 9(2), 249- 267.
Lewis-Hall, F., Williams, T., Panetta, J., & Herrera, J. (2002). Psychiatric illnesses in women: Emerging treatments and research. Washington, DC: American Psychiatric Publishing.
Maldonado, J. R., Butler, L. D., & Spiegel, D. (2002). Treatments for dissociative disorders. In A Guide to Treatments That Work (2nd Ed.). New York: Oxford University Press.
Okugawa, G., Nobuhara, K., Kitashiro, M., Kinoshita, T. (2005). Perospirone for treatment of Dissociative Identity Disorder. Psychiatry and Clinical Neurosciences, 59, 624.
Pasquini, P., Liotti, G., Mazzotti, E., Fassone, G., Picardi, A., & The Italian Group forthe Study of Dissociation. (2002). Risk factors in the early family life of patients suffering from dissociative disorders. Acta Psychiatrica Scandinavica, 105, 110-116.
Reinders,A., Nijenhuis, E., Quak, J., Korf, J., Haaksma, J., Paans, A., Willemsen, A., & den Boer, J. (2006). PsychobiologicalcharacteristicsofDissociativeIdentityDisorder:A symptomprovocationstudy [Abstract]. Biological Psychiatry, 60(7), 730-740.
Rubin, E., & Zorumski, R. (Eds.). (2005). Adult psychiatry (2nd ed). Malden, MA: Blackwell Publishing.
Sno, H., & Schalken, H. (1999). Dissociative identity disorder: diagnosis and treatment in the Netherlands [Abstract]. European Psychiatry, 14(5), 270-277.
Tsai, G., Condie, D., Wu, M. T., & Chang, I. W. (1999). Functional magnetic resonance imaging of personality switches in a woman with Dissociative Identity Disorder. Harvard Review of Psychiatry, 7, 199-122.
Vermetten, E., Schmahl, C., Lindner, S., Loewenstein, R., & Bremner, J. (2006). Hippocampal and amygdalar volumes in Dissociative Identity Disorder. American Journal of Psychiatry, 163, 630–636.
Waller, N., & Ross, C. (1997).The prevalence and biometric structure of pathological dissociation in the general population: Taxometric and behavior genetic findings. Journal of Abnormal Psychology, 106(4), 499-510.
Xiao, Z., Yan, H., Wang, Z., Zou, Z., Xu, Y., Chen, J., Zhang, H., Ross, C., & Keyes, B. (2006). Trauma and dissociation in China. American Journal of Psychiatry, 163(8), 1388-1391.