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Think of dissociative amnesia as the mind 'locking a filing cabinet drawer' containing memories too distressing to access, while every other drawer in the office keeps working normally.

• Dissociative (psychogenic) amnesia is a sudden, functional disruption of the retrieval of autobiographical memory, precipitated by severe psychological stress or trauma, in the absence of a structural, toxic, or organic cause.
• Memory encoding and storage are preserved intact; the deficit lies specifically in conscious retrieval, which is why hypnosisA state of focused attention and relaxation sometimes used therapeutically to alter perception or behaviour.Read more → or a supportive interview can sometimes recover the lost material.
• ICD-11 recognises several patterns of extent: localised (a discrete period), selective (parts of a period), generalised (entire life history), and systematised (a specific category of information, e.g. all memories of one person).
• Dissociative fugue is a specific, more severe variant in which the amnesia is accompanied by purposeful travel away from home and loss of the customary sense of personal identity, sometimes with adoption of a new one.
• Both conditions typically resolve spontaneously, often abruptly, once the precipitating stress is removed or processed, though recovery can occasionally be partial or delayed.

• A 68-year-old woman with no prior psychiatric history and no known cognitive impairment develops a first episode of well-systematised persecutory delusionsA fixed false belief, held with total conviction, that is not shared by the person's culture and is not changed by evidence against it.Read more → and third-person auditory hallucinationsSeeing, hearing, or otherwise sensing things that are not really there.Read more → over several months.
• A 34-year-old man is brought to the emergency department after being found wandering in a town 200 miles from his home.
• A 27-year-old woman presents unable to recall the four months since she discovered her partner's infidelity, while her memory for earlier and more recent events is intact.
• A 41-year-old woman describes a two-week period, following a violent assault, that she cannot recall at all, despite witnesses confirming she continued to attend work and interact normally during that time.

• Unlike Korsakoff syndromeA chronic memory disorder, usually from thiamine deficiency, marked by severe short-term memory loss and confabulation.Read more → or head injury amnesia, there is no confabulationFilling a gap in memory with a made-up answer the person genuinely believes is true, not a deliberate lie.Read more →, no anterograde memory deficit for new information, and no abnormal imaging or metabolic marker.
• Unlike transient global amnesia, which occurs mainly in older adults with vascular risk factors and causes marked anterograde amnesia with repetitive questioning, dissociative amnesia targets autobiographical retrieval and is linked to psychological trauma.
• Unlike malingeringDeliberately faking or exaggerating symptoms for an obvious external gain, such as money or avoiding work.Read more →, there is no identifiable external incentive being consciously pursued, and the presentation is not exaggerated for secondary gain.
• Unlike a complex partial seizure, the episode is not brief and stereotyped, and there is no post-ictal confusion or automatism.

• Assuming any gap in memory after trauma must be dissociative — always exclude organic causes (head injury, intoxication, seizure, encephalitis) first with history, examination, and appropriate investigation.
• Assuming fugue is simply 'amnesia plus wandering' — the defining feature is the loss of the sense of personal identity, not just travel.
• Assuming confabulationFilling a gap in memory with a made-up answer the person genuinely believes is true, not a deliberate lie.Read more → supports dissociative amnesia — confabulation actually points towards an organic amnestic syndrome such as Korsakoff syndromeA chronic memory disorder, usually from thiamine deficiency, marked by severe short-term memory loss and confabulation.Read more →.
• Assuming the patient must be unaware anything is wrong — many patients with localised dissociative amnesia are distressed and aware that a period of time is missing.

• Extract the defining phenomenology, duration, severity and functional-impact clues.
• Match the pattern to the most specific diagnostic or assessment construct.
• Actively test the closest look-alike against the missing or contradictory clue.
• Choose the precise term rather than a broader category that is merely compatible.