December 16, 2013 at 6:52 PM

Jeff, thanks for the great question! Total amnesia of uncertain cause, in an otherwise healthy individual, with amnesia reversal at the end of the episode, as is often portrayed in sitcoms and on TV, is almost non-existent. Drugs, primarily tranquilizers and sleeping pills, often in combination with other recreational drugs and alcohol, cause the vast majority of true temporary amnesia. People under the influence of some sleeping pills can sometimes awaken, walk, drive, and more, for several hours, with no recall of events. Deliberate drug induced amnesia, such as with Rohypnol, the “date rape drug” also called “roofies,” has been used realistically as a major plot point in crime fiction.

Major psychological trauma, such as rape and PTSD, can produce amnesia that is usually limited to the traumatic event. Rape victims, soldiers, or murder witnesses often have delayed recall. Victims may not report crimes for many years, especially childhood trauma, due to amnesia. Witnesses may be unable to identify a suspect, or recall a crime, until years later, complicating arrest and trial. Amnesia induced by psychological trauma is often used as a major plot point in mystery and detective fiction.

Disease can cause specific types of amnesia. TGA, or Transient Global Amnesia, is a rare disorder that causes 12-18 hours of short-term memory loss, with preservation of most long-term memories. TGA patients can only remember the last 15 minutes, but still have most long-term memories intact. Brain damage from trauma, tumors, seizures, stroke, and chronic conditions like Alzheimer’s and senile dementia, cause profound, long term amnesia that is usually progressive and irreversible. Rarely, limited brain damage can produce strange and very specific types of memory disorders; a fact exploited nicely in the movie “50 First Dates.”

Major psychiatric disorders, such as bipolar disease and schizophrenia, can create a dissociative state, where the individual is not aware of self, suffers visual and auditory hallucinations, and takes on new personality traits. This is not actually amnesia, but can lead to a “Dr. Jekyll and Mr. Hyde” situation, with gaps in self-awareness that occur during the psychotic episodes.

Science fiction often uses memory erasure or implantation as a plot point, as with artificial childhoods for humanoid Replicants in the classic “Blade Runner.” The technology to erase memories or create artificial memories does not exist today, but it’s not beyond the realm of possibility for the distant future. Medical fiction and detective fiction should probably stick to known manifestations of amnesia, but I’d certainly give sitcoms a lot of leeway.

H.S. Clark, MD



January 15, 2015 at 6:12 PM
Unless you know differently, my medical mystery / sci fi novel, ARIA: Left Luggage is the only work using infectious amnesia. It doesn't exist but think of the ramifications if it did. Such a What If scenario! I interviewed neurologists to put in accuracy where possible but would appreciate feedback.

Geoff Nelder
thriller, fantasy, scifi writer
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