Conspirators in their own memory loss – findings from 53 patients with “psychogenic amnesia”

A person diagnosed with psychogenic amnesia complains of serious memory problems, sometimes even forgetting who they are, without there being any apparent physical reason for their symptoms – in other words, their condition seems to be purely psychological.

It's a fascinating, controversial diagnosis with roots dating back to Freud's, Breuer's and Charcot's ideas about hysteria and how emotional problems sometimes manifest in dramatic physical ways. Today, some experts doubt that psychogenic amnesia is a real phenomenon, reasoning that there is either an undetected physical cause or the patient is fabricating their memory symptoms.

In a new paper in Brain, a team of British neuropsychologists has reported their findings from a study of 53 patients diagnosed with psychogenic amnesia – one of the largest ever studies of its kind. Michael Kopelman at Kings College, London, and his colleagues conclude that the prognosis (that is, the scope and speed of recovery) for psychogenic amnesia is better than previously realised and that there appear to be four main categories of the condition.

The patients with psychogenic amnesia had all been referred to St Thomas's Hospital in London between 1990 and 2008, and the researchers compared their memory functioning and clinical history with 21 patients with memory disorders with a known physical cause (such as early stage Alzheimer's or hypoxia), and 14 healthy volunteers.

The patients with psychogenic amnesia fell into four distinct categories. There were those who were in a fugue state, who had been wandering lost for days with no recollection of who they are or their past life. "I had a breakdown," said one patient. "My brain decided to close down. I felt as if placed into a grown-up body without knowing the history of the body."

Upon neurological examination, the fugue patients appeared healthy, and their state usually returned to normal within four weeks, though often sooner, and sometimes within hours. After recovery, most of their memories returned, except for a blank gap during the fugue state.

The second category was fugue-to-focal retrograde amnesia. These patients started out in a fugue state – lost and usually with no or little memory of their past and no sense of identity – then as the fugue state resolved, they were left with more persistent memory loss for large periods of their past lives. Their memory gaps seemed to take longer to recover than the fugue patients (sometimes never recovering), though with a relative sparing of more recent memories.

The third category was focal retrograde amnesia. These patients had a severe loss of memory for large periods of their lives, or their entire lives, sometimes a temporary loss of identity, but there was no fugue period involving wandering. The onset was often a mild neurological event (such as a minor stroke) or minor head injury, but one "insufficient to account for the severity of the retrograde memory loss". Similar to the fugue-to-focal retrograde amnesia category, these patients' memory loss was more prolonged than the fugue patients, but with a relative sparing of more recent memories.

And finally, some of the patients fell into a category the researchers called "gaps in memory" – they didn't have a wandering period, loss of personal identity was also rare, and their one or more periods of memory loss were discrete, often tied to a specific traumatic experience (and often associated with PTSD).

At six months follow up, the fugue patients and to a lesser extent, the focal retrograde amnesia patients, showed good improvement. "In summary, the prognosis in psychogenic amnesia appears better than the previous literature suggests," the researchers said.

Comparing the psychogenic patients with the neurological and healthy controls, the psychogenic group were more likely to have suffered a past head injury (though not of sufficient seriousness to explain their memory problems); they were more likely to have a diagnosis of depression; to have a history of family or relationship problems, or employment problems; problems in childhood; and/or a history of alcohol or drug problems.

The finding that the psychogenic patients were more likely to have a history of head injury than the neurological controls is particularly surprising. Kopelman's team said "this may predispose some individuals to developing psychogenic amnesia at a later time of severe precipitating crisis."

A debate about psychogenic amnesia that dates back to Freud is whether the process of memory loss is deliberate or subconscious. Kopelman and his team observed that their findings were more consistent with there being a conscious, deliberate element to the condition (as first proposed by Freud and Josef Breuer, though Freud later changed his position). For instance, some of the patients in the new study made comments like: "It's like a box locked away, and I don't really want to open it" and "I put things in boxes … I know the memories are there … but cannot get access to them."

The current thinking of Kopelman and others is that the deliberate memory suppression of psychogenic amnesia is often brought about by stressful crises in life, and that the deliberate forgetting manifests in genuine neurological processes that really do interfere with memory and even personal identity. Kopelman and his team conclude by quoting the Cambridge University psychologists Michael Anderson and Simon Hanslmayr: "Control mechanisms mediated by the prefrontal cortex interrupt mnemonic function and impair memory … We are … conspirators in our own forgetting."