Dissociative amnesia is classified by the Diagnostic and Statistical Manual of Mental Disorders , 4th Edition, Text Revision, also known as the DSM-IV-TR as one of the dissociative disorders, which are mental disorders in which the normally well-integrated functions of memory, identity, perception, or consciousness are separated (dissociated). The dissociative disorders are usually associated with trauma in the recent or distant past, or with an intense internal conflict that forces the mind to separate incompatible or unacceptable knowledge, information, or feelings. In dissociative amnesia, the continuity of the patient’s memory is disrupted. Patients with dissociative amnesia have recurrent episodes in which they forget important personal information or events, usually connected with trauma or severe stress. The information that is lost to the patient’s memory is usually too extensive to be attributed to ordinary absentmindedness or forgetfulness related to aging. Dissociative amnesia was formerly called “psychogenic amnesia”.
Amnesia is a symptom of other medical and mental disorders; however, the patterns of amnesia are different, depending on the cause of the disorder. Amnesia associated with head trauma is typically both retrograde (the patient has no memory of events shortly before the head injury) and anterograde (the patient has no memory of events after the injury). The amnesia that is associated with seizure disorders is sudden onset. Amnesia in patients suffering from delirium or dementia occurs in the context of extensive disturbances of the patient’s cognition (knowing), speech, perceptions, emotions, and behaviors. Amnesia associated with substance abuse, which is sometimes called “blackouts” typically affects only short-term memory and is irreversible. In dissociative amnesia, in contrast to these other conditions, the patient’s memory loss is almost always anterograde, which means that it is limited to the period following the traumatic event(s). In addition, patients with dissociative amnesia do not have problems learning new information.
Dissociative amnesia as a symptom occurs in patients diagnosed with dissociative fugue and dissociative identity disorder . If the patient’s episodes of dissociative amnesia occur only in the context of these disorders, a separate diagnosis of dissociative amnesia is not made.
atients with dissociative amnesia usually report a gap or series of gaps in their recollection of their life history. The gaps are usually related to episodes or abuse or equally severe trauma, although some persons with dissociative amnesia also lose recall of their own suicide attempts, episodes of self-mutilation, or violent behavior.
Five different patterns of memory loss have been reported in patients with dissociative amnesia:
- Localised. The patient cannot recall events that took place within a limited period of time (usually several hours or 1–2 days) following a traumatic event. For example, some survivors of the World Trade Center attacks do not remember how they got out of the damaged buildings or what streets they took to get away from the area.
- Selective. The patient can remember some, but not all of the events that took place during a limited period of time. For example, a veteran of D-Day (June 6, 1944) may recall some details, such as eating a meal on the run or taking prisoners, but not others (seeing a close friend hit or losing a commanding officer).
- Generalised. The person cannot recall anything in his/her entire life. Persons with generalized amnesia are usually found by the police or taken by others to a hospital emergency room.
- Continuous. The amnesia covers the entire period without interruption from a traumatic event in the past to the present.
- Systematised. The amnesia covers only certain categories of information, such as all memories related to a certain location or to a particular person.
Most patients diagnosed with dissociative amnesia have either localised or selective amnesia. Generalized amnesia is extremely rare. Patients with generalized, continuous, or systematized amnesia are usually eventually diagnosed as having a more complex dissociative disorder, such as dissociative identity disorder (DID).