From Nature:
The idea of repressed memory — when traumatic events are wiped from a person’s conscious memory but resurface years later — has had a chequered past. Some have cited it as evidence in court, yet others dismiss it as nothing more than psychiatric folklore. A new study adds a literary layer of evidence to the debate. To see how long the idea of repressed memories have been around, a group of psychologists and literature scholars turned to historical writings.
They could not find a single description of repressed memory, also referred to as dissociative amnesia, in fiction or factual writing before 1800. Harrison Pope of Harvard Medical School in Boston, Massachusetts, and his colleagues harnessed the power of the Internet to gather information, advertising on more than 30 websites and discussion boards a US$1,000 prize to the first person who could find an example of repressed memory after a traumatic event in a work published before 1800.
More here.