Cause

Research has shown that multiple personality is most probably caused by severe
childhood abuse, usually both physical and sexual. Psychotherapists
who specialize in treating disorders caused by trauma hypothesize that the
human mind or personality divides to cope with the terror of the trauma. It
is as if one part of the mind handles the abuse to protect another part of the
mind from the pain. This splitting of consciousness is a psychological defense
called dissociation. Instead of memory, bodily sensation, emotions,
and thoughts all being associated with an experience (which is the normal
process of human experience), these aspects lose their association and seem
to separate. A common example would be that a person who was sexually
abused as a child loses the memory of those events and may have no recall of
them until later in adulthood. In this case, the whole experience is dissociated.
For example, in multiple personality, a so-called alternate personality
(“alter” for short) named Ann experienced the abuse, while alter Jane, who
deals with normal, everyday living, was not abused. Thus, Jane has no memories
of abuse. A variation is that only certain aspects of the experience are
dissociated, so that, for instance, the abused person has the memory that the
sexual abuse happened but has no emotions regarding the pain and trauma
of it. Freud coined the term “repression” to describe the process by which
emotions that are too threatening to be admitted into consciousness are
pushed into the unconscious. 560