The term is used to describe memories that have been dissociated from awareness as well as those that have been repressed without dissociation. Repressed memory syndrome, the clinical term used to describe repressed memories, is often compared to psychogenic amnesia, and some sources compare the two as equivalent.
According to the theory's proponents, repressed memories may sometimes be recovered years or decades after the event, most often spontaneously, triggered by a particular smell, taste, or other identifier related to the lost memory, or via suggestion during psychotherapy.
The existence of repressed memories is a controversial topic in psychology; some studies have concluded that it can occur in victims of trauma, while others dispute it.
According to the American Psychological Association, it is not currently possible to distinguish a true repressed memory from a false one without corroborating evidence.
The concept was originated by Sigmund Freud in his 1896 essay Zur Ätiologie der Hysterie ("On the etiology of hysteria"). Freud abandoned his theory between 1897 and 1905, replacing it during 1920-1923 with his impulse-based concept of Ego, super-ego, and id. Friedrich Nietzsche was the first to suggest an active, conscious thought management method in the second essay of his On the Genealogy of Morals as a necessary fundament of efficiency, responsibility, and maturity.
Van der Kolk and Fisler's research shows that traumatic memories are retrieved, at least at first, in the form of mental imprints that are dissociated. These imprints are of the affective and sensory elements of the traumatic experience. Clients have reported the slow emergence of a personal narrative that can be considered explicit (conscious) memory. The level of emotional significance of a memory correlates directly with the memory's veracity. Studies of subjective reports of memory show that memories of highly significant events are unusually accurate and stable over time. The imprints of traumatic experiences appear to be qualitatively different from those of nontraumatic events. Traumatic memories may be coded differently than ordinary event memories, possibly because of alterations in attentional focusing or the fact that extreme emotional arousal interferes with the memory functions of the hippocampus.
Although the science of repressed memory is limited, a few studies have suggested that memories of trauma that are forgotten and later recalled have a similar accuracy rate as trauma memories that had not been forgotten.
It has been speculated that repression may be one method used by individuals to cope with traumatic memories, by pushing them out of awareness (perhaps as an adaptation via psychogenic amnesia) to allow a child to maintain attachment to a person on whom they are dependent for survival. Researchers have proposed that repression can operate on a social level as well.
The existence of repressed memories has not been completely accepted by mainstream psychology, nor unequivocally proven to exist, and some experts in the field of human memory feel that no credible scientific support exists for the notions of repressed/recovered memories. One research report states that a distinction should be made between spontaneously recovered memories and memories recovered during suggestions in therapy.
In a 1996 ruling, a US District Court allowed repressed memories entered into evidence in court cases. Jennifer Freyd writes that Ross Cheit's case of suddenly remembered sexual abuse is one of the most well-documented cases available for the public to see. Cheit prevailed in two lawsuits, located five additional victims and tape-recorded a confession.