Dissociative Amnesia

Dissociative amnesia is a dissociative disorder characterized by temporary memory gaps in response to stressful events. Dissociative amnesia can be subclassified as generalized versus localized or continuous versus systematized. The most common type is the localized loss of memory about certain life events that are usually traumatic and unpleasant. Management involves psychotherapy tailored to recovering lost memories in a safe fashion.

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Overview

Definition

Dissociative amnesia is a potentially reversible memory impairment that primarily affects autobiographical information, often following stressful or traumatic events

Types of memory

  • Autobiographical: details regarding events in person’s life, including events that have happened and their cognitive, emotional, and motivational impact 
  • Semantic: memory of facts, concepts, objects, words, and definitions
  • Episodic: memory of specific events  
  • Procedural: memory of how certain procedures are carried out

Epidemiology

  • Lifetime prevalence: approximately 2%–6%
  • Higher incidence among women 
  • Usually arise in late adolescence and young adulthood
  • Comorbid conditions:
    • Substance use disorder
    • History of trauma 
    • Major mood disorders
    • Conversion disorder

Pathogenesis

  • Environmental factors: 
    • Events triggering intolerable and unacceptable emotions
    • Emotions are often triggered by trauma or by betrayal by someone the patient trusted.
    • These triggers are thought to influence how the event is remembered.
  • Genetic factors: 
    • Genes and environmental factors that influence their expression (epigenetic model)
    • A stressful or traumatic event during childhood or later in life can trigger expression of genetic diathesis that otherwise would have been suppressed.
    • 50% of the variance in the development of dissociative symptoms could be accounted for by genetic factors.
  • Neurobiologic factors:
    • Temporal, hippocampal, and occipital areas are associated with autobiographical memory 
    • If any of these brain regions are affected, it can lead to dissociation.

Diagnosis and Clinical Features

Diagnosis

Diagnosis is clinical, based on meeting specific criteria:

  • Criteria:
    • An impairment in the ability to recall important autobiographical information inconsistent with normal forgetting
    • Symptoms cause marked distress or impairment in social and occupational functioning.
  • Exclusion:
    • Impairment not secondary to substance use or other neurologic/medical conditions
    • Impairment is not secondary to other psychiatric disorders.

Clinical features

  • Classic presentation: 
    • Dissociative symptoms in the setting of extreme trauma
    • Patient cannot recall:
      • Who they are
      • Where they have been
      • What they have done at a specific time
  • Types of dissociative amnesia: 
    • Localized amnesia: inability to recall autobiographical memory of a specific period of time or specific event
    • Selective amnesia: inability to recall parts of an event
    • Systematized: inability to remember certain categories of memory (e.g., inability to recall home life during 3rd grade, but able to recall school)
    • Continuous: inability to remember successive events as they occur (anterograde dissociative amnesia).
    • Generalized (global) amnesia: inability to recall the entirety of life history, usually accompanied by loss of person’s identity

Management

  • Goal is to restore patient’s lost memories safely: Risk of suicide is initially increased when patient recalls traumatic events or memories.
  • Psychotherapy: attempts to identify cognitive distortions based in patient’s history of trauma: 
    • 1st-line therapy
    • Examples:
      • Cognitive therapy
      • Hypnosis and hypnotherapy
      • Group therapy 
  • Pharmacotherapy: 
    • Not indicated unless used for treatment of comorbidities (management of the associated depression with antidepressants) 
    • Drug-assisted interviews: 
      • Hypnotic agents  (barbiturates or benzodiazepines) can help in the retrieval of certain lost memories.
      • Retrieved memories are then reprocessed when the patient is in the usual conscious state.

Differential Diagnosis

  • Nonpathologic dissociation: dissociation normally experienced during daily activities (i.e., arriving at a destination in your vehicle without recalling the details of the drive). Nonpathologic dissociation is distinguished from dissociative amnesia because the patient does not experience feelings of distress or functional impairment.
  • Transient global amnesia: form of temporary anterograde amnesia with sudden onset often triggered by highly stressful events. This impairment is associated with disorientation, but patients do not lose awareness of self. The symptoms resolve without any intervention and without any lasting neurologic deficits. The distinguishing features between this diagnosis and dissociative amnesia is the age at onset (usually ≥ 50 years for transient global amnesia) as well as preservation of personal memories.
  • Dementia: group of chronic disorders of the mental processes caused by brain disease or injury, marked by memory disorders, personality changes, and impaired reasoning. The patient with dementia is upset by memory loss and tries to recall memories, whereas the patient with dissociative amnesia is not upset and is not trying to recall memories. Dementia usually is prevalent in populations that are much older than those with dissociative amnesia. 
  • Dissociative identity disorder (DID): disorder marked by the presence of ≥ 2 distinct personality identities in the patient, with each personality having their own memories. The patient switches between personalities rapidly, especially under stress. Dissociative identity disorder is associated with a history of childhood trauma or abuse similar to those with dissociative amnesia. Unlike dissociative amnesia, memory impairments in DID include amnesia for normal everyday events or recurrent blackouts. 
  • Acute stress disorder: stress reactions displayed after an individual has experienced a traumatic event. Symptoms last > 3 days, but < 1 month and include reexperiencing the event as flashbacks or nightmares, avoidance of reminders of the event, irritability, hyperarousal, and poor memory and concentration. When a patient exhibits amnesia that extends beyond the time frame of the event, the diagnosis of dissociative amnesia can be made.

References

  1. Sadock BJ, Sadock VA, Ruiz P. (2014). Dissociative disorders. Chapter 12 of Kaplan and Sadock’s Synopsis of Psychiatry: Behavioral Sciences/Clinical Psychiatry. Philadelphia: Lippincott Williams and Wilkins, pp. 451–464.
  2. Spiegel D, Loewenstein RJ, Lewis-Fernández R, Sar V, Simeon D, Vermetten E, Cardeña E, Dell PF. (2011). Dissociative disorders in DSM-5. Depress Anxiety 28:824–52. https://pubmed.ncbi.nlm.nih.gov/21910187/ 
  3. Waller NG, Ross CA. (1997). The prevalence and biometric structure of pathological dissociation in the general population: taxometric and behavior genetic findings. J Abnorm Psychol. https://pubmed.ncbi.nlm.nih.gov/9358680/ 
  4. Rapaport D. (1942). Emotions and Memory. Baltimore: Lippincott Williams and Wilkins.

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