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Dissociative amnesia

Amnesia (or amnaesia in Commonwealth English) is a condition in which memory is disturbed. The causes of amnesia are organic or functional. Organic causes include damage to the brain, through trauma or disease, or use of certain (generally sedative) drugs. Functional causes are psychological factors, such as defense mechanisms. Hysterical post-traumatic amnesia is an example of this. Amnesia may also be spontaneous, in the case of transient global amnesia. This global type of amnesia is more common in middle-aged to elderly people, particularly males, and usually lasts less than 24 hours. more...

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Types of amnesia

  • In anterograde amnesia, new events are not transferred to long-term memory, so the sufferer will not be able to remember anything that occurs after the onset of this type of amnesia for more than a few moments. The complement of this is retrograde amnesia, where someone will be unable to recall events that occurred before the onset of amnesia. The terms are used to categorise patterns of symptoms, rather than to indicate a particular cause or etiology. Both categories of amnesia can occur together in the same patient, and commonly result from damage to the brain regions most closely associated with episodic/declarative memory: the medial temporal lobes and especially the hippocampus.
  • Traumatic amnesia is generally due to a head injury (fall, knock on the head). Traumatic amnesia is often transient; the duration of the amnesia is related to the degree of injury and may give an indication of the prognosis for recovery of other functions. Mild trauma, such as a car accident that could result in no more than mild whiplash, might cause the occupant of a car to have no memory of the moments just before the accident due to a brief interruption in the short/long-term memory transfer mechanism. "Traumatic amnesia" is also sometimes used to refer to long-term repressed memory that is the result of psychological trauma.
  • Long-term alcoholism can cause a type of memory loss known as Korsakoff's syndrome. This is caused by brain damage due to a Vitamin B1 deficiency and will be progressive if alcohol intake and nutrition pattern are not modified. It will usually improve little over time even if they are. Other neurological problems are likely to be present.
  • Lacunar amnesia is the loss of memory about one specific event.
  • Fugue state is also known as dissociative fugue. It is caused by psychological trauma and is usually temporary. The Merck Manual defines it as "one or more episodes of amnesia in which the inability to recall some or all of one's past and either the loss of one's identity or the formation of a new identity occur with sudden, unexpected, purposeful travel away from home" .
  • Childhood amnesia (also known as Infantile amnesia) is the common inability to remember events from your own childhood. Whilst Sigmund Freud attributed this to sexual repression, others have theorised that this may be due to language development or immature parts of the brain.
  • Global amnesia is total memory loss. This may be a defence mechanism which occurs after a traumatic event. Post-traumatic stress disorder can also involve the spontaneous, vivid retrieval of unwanted traumatic memories. It is believed that Mauritania's Silent Flute Man suffered from this condition.
  • Posthypnotic amnesia is where events during hypnosis are forgotten, or where past memories are unable to be recalled.
  • Psychogenic amnesia is when one loses the ability to remember who oneself is. It is a common type of amnesia in popular culture; it may or may not be a real phenomenon.
  • Source amnesia is a memory disorder in which someone can recall certain information, but they do not know where or how they obtained it.
  • Memory distrust syndrome is a term invented by the psychologist Gisli Gudjonsson to describe a situation where someone is unable to trust their own memory.


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Dissociation/Dissociative disorders
From Gale Encyclopedia of Psychology, 4/6/01

Dissociation, or the feeling of being detached from the reality of one's body, can be categorized into two types: depersonalization and derealization. Depersonalization is highlighted by a sense of not knowing who you are, or of questioning long-held beliefs about who you are. In derealization, persons perceive reality in a grossly distorted way. Psychologists have identified several types of disorders based on these feelings. These include depersonalization disorder, dissociative fugue, dissociative amnesia, dissociative trance disorder, and dissociative identity disorder (also known as multiple personality syndrome), among others.

Depersonalization disorder is a condition marked by a persistent feeling of not being real. The DSM-IV describes its symptoms as "persistent or recurrent experiences of feeling detached from, and as if one is an outside observer of, one's mental processes or body (e.g., feeling like one is in a dream)." While many people have experienced a similar feeling, persons actually suffering from this disorder are so overwhelmed by these feelings that they are unable to function normally in society. It is also critical to point out that in order to be diagnosed as having this disorder, these feelings cannot be caused by some specific drug or event. Depersonalization disorder, by itself, is a rare disorder, and, in fact, many of its symptoms are also symptomatic of other more common disorders, such as acute stress disorder and panic attacks.

Dissociative fugue is a strange phenomena in which persons will be stricken with a sudden memory loss that prompts them to flee their familiar surroundings. These flights are usually caused by some traumatic event. People suffering from this disorder will suddenly find themselves in a new surrounding, hundreds or even thousands of miles from their homes with no memories of the weeks, months, or even years that have elapsed since their flight. Incidence of dissociative fugue rarely appear until after adolescence and usually before the age of 50. Once a person has fallen into the behavior, however, it is more likely that it will recur.

Dissociative amnesia describes the condition of suddenly losing major chunks of memory. There are two types of this disorder: generalized amnesia, in which a person cannot remember anything about their lives, and localized amnesia, a common disorder in which a person forgets pieces of their identity but retains an overall understanding of who they are. Dissociative amnesia is generally caused by some traumatic event, such as a natural disaster, a violent crime, or war. In these instances, it is an adaptive mechanism that allows a person to continue his or her life without having to deal with an utterly horrific memory.

Dissociative trance disorder describes the trance-state that people experience in various kinds of religious ceremonies. Such people generally perform feats that would normally cause injury or severe pain-such as walking on hot coals-but because of their dissociated mental state, they are not harmed. This is a curious subcategory in that the condition is not considered a "disorder" in many cultures of the world. Western psychiatrists are divided as to whether this should really be considered a "disorder," since the word has negative implications. It has been proposed, however, that future editions of the DSM specify a diagnosis of trance and possession disorder as one of several dissociative disorders.

Gale Encyclopedia of Psychology, 2nd ed. Gale Group, 2001.

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