The cardinal feature of the dissociative disorders is an acute or gradual, transient or persistent, disruption of consciousness, perception, memory or awareness, not associated with physical disease or organic brain dysfunction, and severe enough to cause distress or impairment. Three types are described in DSM-5, and there is a miscellaneous fourth and fifth group. The distinction between these types may be blurred, particularly when patients exhibit symptoms from more than one type.
Epidemiologic data on dissociative disorders are patchy. The prevalence of dissociative identity disorder is disputed but probably low. Case reports suggest a female-to-male ratio of at least 5:1. This ratio might be exaggerated, because males with dissociative disorder, who are likely to be episodically violent, are likely to be directed to the correctional system. Dissociative identity disorder is found in all ethnic groups, though mainly in whites, and in all socioeconomic groups. Studies of combat soldiers have found a prevalence of dissociative amnesia of 5–8%. Depersonalization is a frequent concomitant of anxiety disorders, posttraumatic stress disorder, and severe depression. Up to one half of college students claim to have experienced depersonalization at some time in their lives. It has been reported that 80% of psychiatric inpatients suffer from depersonalization, but in only 12% is the symptom long lasting, and in no case is it the only symptom. The sex ratio is equal.
Normal dissociation is an adaptive defense used to cope with overwhelming psychic trauma. It is commonly encountered during and after civilian disasters, criminal assault, sudden loss, and war. In normal dissociation, the individual's perception of the traumatic experience is temporarily dulled or dispelled from consciousness. Normal dissociation prevents other vital psychological functions from being overwhelmed by the traumatic experience. The capacity to dissociate, as evidenced by susceptibility to hypnosis, is widely distributed among normal people. However, it is unclear whether pathologic dissociation is an extreme or more enduring form of normal dissociation (i.e., whether there is a continuum of dissociation between normal and abnormal) or whether the pathologic form is distinctive. Recent studies of trauma subjects have found only a low correlation between hypnotizability and measures of dissociation.
Theories concerning the basis of pathologic dissociation can be classified as psychological, neurocognitive, traumagenic, and psychosocial.
1. Psychological theories
Janet postulated that some people have a constitutional "psychological insufficiency" that renders them prone to dissociate in the face of frightening experiences. At that time, memories associated with "vehement emotions" become separated or dissociated from awareness in the form of subconscious fixed ideas, which are not integrated into memory. Rather, they remain latent and are prone to return to consciousness as psychological automatisms such as hysterical paralyses, anesthesias, and somnambulisms (trance states).
Breuer and Freud suggested that hysterical patients ...