It is therefore unknown if there is a commonality between all dissociative experiences, or if the range of mild to severe symptoms is a result of different etiologies and biological structures. Other terms used in the literature, including personality, personality state, identity, ego state, and amnesia, also have no agreed upon definitions. Multiple competing models exist that incorporate some non-dissociative symptoms while excluding dissociative ones.Due to the lack of consensus regarding terminology in the study of DID, several terms have been proposed. One is ego state (behaviors and experiences possessing permeable boundaries with other such states but united by a common sense of self), while the other term is alters (each of which may have a separate autobiographical memory, independent initiative and a sense of ownership over individual behavior).Ellert Nijenhuis and colleagues suggest a distinction between personalities responsible for day-to-day functioning (associated with blunted physiological responses and reduced emotional reactivity, referred to as the "apparently normal part of the personality" or ANP) and those emerging in survival situations (involving fight-or-flight responses, vivid traumatic memories and strong, painful emotions – the "emotional part of the personality" or EP). "Structural dissociation of the personality" is used by Otto van der Hart and colleagues to distinguish dissociation they attribute to traumatic or pathological causes, which in turn is divided into primary, secondary and tertiary dissociation.
"The DSM-5 diagnostic manual states that DID is "associated with overwhelming experiences, traumatic events, and/or abuse during childhood". (p 294) Other risk factors reported include childhood neglect, childhood medical procedures, war, terrorism, and childhood prostitution. (p 295) Dissociative disorders frequently occur after trauma, and the DSM5 places them after the trauma and stressor-related disorders to reflect this close relationship. (p 291) Disturbed and altered sleep has also been suggested as having a role in dissociative disorders in general and specifically in DID, alterations in environments also largely affecting the DID patient. Developmental trauma
People diagnosed with DID often report that they have experienced physical or sexual abuse during childhood (although the accuracy of these reports has been disputed); others report overwhelming stress, serious medical illness or other traumatic events during childhood. They also report more historical psychological trauma than those diagnosed with any other mental illness. Severe sexual, physical, or psychological trauma in childhood has been proposed as an explanation for its development; awareness, memories and emotions of harmful actions or events caused by the trauma are removed from consciousness, and alternate personalities or subpersonalities form with differing memories, emotions and behavior. DID is attributed to extremes of stress or disorders of attachment.