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7.2 Dissociative Amnesia

Section Learning Objectives

  • Describe how dissociative amnesia presents itself.
  • Describe the epidemiology of dissociative amnesia.
  • Indicate which disorders are commonly comorbid with dissociative amnesia.
  • Describe factors that may contribute to the etiology of dissociative amnesia.
  • Describe the treatment of dissociative amnesia.

7.2.1 Clinical Description

Dissociative amnesia is identified by amnesia for autobiographical information, particularly for traumatic events. This type of amnesia is different from what one would consider a permanent amnesia in that the information was successfully stored in memory, however, the individual cannot retrieve it. Additionally, individuals experiencing permanent amnesia often have a neurobiological cause, whereas dissociative amnesia does not (APA, 2013).

There are a few types of amnesia that people with dissociative amnesia can experience. Localized amnesia, the most common type of dissociative amnesia, is the inability to recall events during a specific period of time. The length of time within a localized amnesia episode can vary—it can be as short as the time immediately surrounding a traumatic event, to months or years, should the traumatic event occur that long (as commonly seen in abuse and combat situations). Selective amnesia is in a sense, a component of localized amnesia in that the individual can recall some, but not all, of the details during a specific time period. For example, a soldier may experience dissociative amnesia during the time they were deployed, yet still, have some memories of positive experiences such as celebrating Thanksgiving dinner or Christmas dinner with their unit. The onset of localized and selective amnesia may immediately follow the acute stress or be delayed for hours, days, or longer.

Conversely, some individuals experience generalized amnesia where they have a complete loss of memory of their entire life history, including their own identity. Individuals who experience this type of amnesia experience deficits in both semantic and procedural knowledge. This means that individuals have no common knowledge of the world (i.e. cannot identify songs, the current president, or names of colors) nor do they have the ability to engage in learned skills (i.e. typing shoes, driving car). The onset of generalized amnesia is typically acute.

While generalized amnesia is extremely rare, it is also extremely frightening. The onset is acute, and the individual is often found wandering in a state of disorientation. Many times, these individuals are brought into emergency rooms by law enforcement following a dangerous situation such as an individual walking aimlessly on a busy road.

Dissociative fugue is considered to be the most extreme type of dissociative amnesia where not only does an individual forget personal information, but they also flee to a different location (APA, 2013). The degree of the fugue varies among individuals – with some experiencing symptoms for a short time (only hours) to others lasting years, affording individuals to take on new identities, careers, and even relationships. Similar to their sudden onset, dissociative fugues also end abruptly. Post dissociative fugue, the individual generally regains most of their memory. Emotional adjustment after the fugue is dependent on the time the individual spent in the fugue – with those having been in a fugue state longer experiencing more emotional distress than those who experienced a shorter fugue (Kopelman, 2002).

7.2.2 Epidemiology

A large community sample suggested dissociative amnesia occurs in approximately 1.8% of the population with females being about 2.5 times more likely to be diagnosed than males (APA, 2013). Similar to trauma-related disorders, it is believed that more women experience dissociative amnesia due to the increased chances of a woman to experience significant stress/trauma compared to that of men.

7.2.3 Comorbidity

Given that dissociative amnesia is often precipitated by a traumatic experience, many people develop PTSD after the traumatic events are finally recalled. Similarly, a wide range of emotions related to their inability to recall memories during the episode often presents once their memories return (APA, 2013). These emotions often contribute to the development of a depressive episode.

Due to the rarity of these disorders with respect to other mental health disorders, it is often difficult to truly determine comorbid diagnoses. There has been some evidence of comorbid somatic symptom disorder and conversion disorder. Furthermore, dependent, avoidant, and borderline personality disorders have all been suspected as co-occurring disorders among the dissociative disorder family.

7.2.4 Etiology Biological

As previously indicated, heritability rates for dissociative experiences range from 50-60% (Pieper, Out, Bakermans-Kranenburg, Van Ijzendoorn, 2011). However, it is suggested that the combination of genetic and environmental factors may play a larger role in the development of dissociative disorders than genetics alone (Pieper, Out, Bakermans-Kranenburg, Van Ijzendoorn, 2011). Cognitive

One proposed cognitive theory of dissociative amnesia proposed by Kopelman (2000) is that the combination of psychological stress and various other biopsychosocial predispositions affects the frontal lobe’s executive system’s ability to retrieve autobiographical memories (Picard et al., 2013). Neuroimaging studies have supported this theory by showing deficits to several prefrontal regions, which is one area responsible for memory retrieval (Picard et al., 2013).  Despite these findings, there is still some debate over which specific brain regions within the executive system are responsible for the retrieval difficulties, as research studies have reported mixed findings. Environmental/Behavioral

Severe trauma and/or stress commonly precipitate the disorder. The most common precipitating stressors for fugues are marital discord, financial and occupational problems, natural disasters, and combat in war. The likelihood that dissociative amnesia is experienced increases with higher numbers of adverse childhood experiences (e.g., physical and/or sexual abuse), and more severe and frequent interpersonal violence. According to the behavioral perspective, the amnesia is negatively reinforced by avoiding/removing the distressing thoughts and feelings associated with the trauma/stressor. Psychodynamic

The psychodynamic theory of dissociative amnesia assumes that dissociative disorders are caused by an individual’s repressed thoughts and feelings related to an unpleasant or traumatic event (Richardson, 1998). In blocking, or dissociating from, these thoughts and feelings, the individual is subconsciously protecting himself from painful memories.

7.2.5 Treatment

Treatment for dissociative amnesia is limited in part because many individuals recover on their own without any type of intervention. Occasionally treatment is sought out after recovery due to the traumatic nature of memory loss. Further, the rarity of the disorder has offered limited opportunities for research on both the development and effectiveness of treatment methods. While there is no evidence-based treatment for dissociative amnesia, both hypnosis and treatment with barbituates have been shown to produce some positive effects in clients with dissociative amnesia.

Hypnosis. One theory of dissociative amnesia is that it is a form of self-hypnosis and that individuals hypnotize themselves to forget information or events that are unpleasant (Dell, 2010). Based on this theory, one type of treatment that has routinely been implemented for individuals with dissociative amnesia is hypnosis. Through hypnosis, the clinician can help the individual contain, modulate, and reduce the intensity of the amnesia symptoms, thus allowing them to process the traumatic or unpleasant events underlying the amnesia episode (Maldonadao & Spiegel, 2014). To do this, the clinician will encourage the client to think of memories just prior to the amnesic episode as though it was the present time. The clinician will then slowly walk them through the events during the amnesic time period in efforts to reorient the individual to experience these events. This technique is essentially a way to encourage a controlled recall of dissociated memories, something that is particularly helpful when the memories include traumatic experiences (Maldonadao & Spiegel, 2014).

Another form of “hypnosis” is the use of barbiturates, also known as “truth serums,” to help relax the individual and free their inhibitions. Although not always effective, the theory is that these drugs reduce the anxiety surrounding the unpleasant events enough to allow the individual to recall and process these memories in a safe environment (Ahern et al., 2000).



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