Repression is a key concept of psychoanalysis, where it is understood as a defence mechanism that "ensures that what is unacceptable to the conscious mind, and would if recalled arouse anxiety, is prevented from entering into it." According to psychoanalytic theory, repression plays a major role in many mental illnesses, and in the psyche of the average person.

American psychologists began to attempt to study repression in the experimental laboratory around 1930. However, psychoanalysts were at first uninterested in attempts to study repression in laboratory settings, and later came to reject them. Most psychoanalysts concluded that such attempts misrepresented the psychoanalytic concept of repression.