Repressed memory is an alleged psychiatric phenomenon which involves an inability to recall autobiographical information, usually of a traumatic or stressful nature. The concept originated in psychoanalytic theory where repression is understood as a defense mechanism that excludes painful experiences and unacceptable impulses from consciousness. Repressed memory is a controversial concept, particularly in legal contexts where it has been used to impugn individuals unfairly and inaccurately, leading to substantial harm. At the same time, an American Psychological Association working group indicated that while "most people who were sexually abused as children remember all or part of what happened to them, it is possible for memories of abuse that have been forgotten for a long time to be remembered". Although Sigmund Freud later revised his theory, he initially held that memories of childhood sexual trauma were often repressed (could not be recalled later in life) yet the traumas unconsciously influenced behavior and emotional responding.
Despite widespread belief in the phenomenon of repressed memories among laypersons and clinical psychologists, most research psychologists who study the psychology of memory dispute that repression ever occurs at all. While some psychologists believe that repressed memories can be recovered through psychotherapy (or may be recovered spontaneously, years or even decades after the event, when the repressed memory is triggered by a particular smell, taste, or other identifier related to the lost memory), experts in the psychology of memory argue that, rather than promoting the recovery of a real repressed memory, psychotherapy is more likely to contribute to the creation of false memories.
In part because of the intense controversies that arose surrounding the concepts of repressed and recovered memories, many clinical psychologists stopped using those terms and instead adopted the term dissociative amnesia to refer to the purported processes whereby memories for traumatic events become inaccessible, and the term dissociative amnesia can be found in the DSM-5, where it is defined as an "inability to recall autobiographical information. This amnesia may be localized (i.e., an event or period of time), selective (i.e., a specific aspect of an event), or generalized (i.e., identity and life history)." The change in terminology, however, has not made belief in the phenomenon any less problematic according to experts in the field of memory. Clinical psychologist Richard McNally stated: "The notion that traumatic events can be repressed and later recovered is the most pernicious bit of folklore ever to infect psychology and psychiatry. It has provided the theoretical basis for 'recovered memory therapy'—the worst catastrophe to befall the mental health field since the lobotomy era."