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DID is most often caused by early sexual child abuse. This child abuse is often intolerable, so much so that the person forgets these events and develops another personality so that the abuse does not have to be dealt with. The alternate personality is a defense mechanism. When someone has DID they feel confused. They do not know why or when they have done a certain thing nor with or to whom. There are some early signs of DID, but they are often mistaken for other disorders such as post-traumatic stress syndrome, schizophrenia, and/or bi-polar disease (manic-depression).
These personalities have the ability to control the person and make them do things that they do not remember or would normally not do which is sometimes known as tunnel vision. Sybil is often depicted in situations where she seems to be waking from a dream; she is too afraid to face things, i.e. the color green reminds her of her mothers apron, classical music renders her uncontrollable because of the classical music played by her mother during waiting periods between abuse, she awakens only to seem disoriented, and confused. She experiences loss of time, and frequently refers to her watch when confronted by the doctor. When someone has DID, they do not realize when another personality is in control or what they are doing. .
Diagnosis of Disassociative Identity Disorder is a complicated process. It involves many psychological tests on the patient as well as preliminary therapy to accurately determine if the patient has DID. Treatments include hypnotherapy, memory therapy, psychotherapy, and inpatient treatment. In hypnotherapy (hypnosis) sometimes DID is discovered when the person is there for a different treatment. Hypnotherapy can also be used for memory retrieval. .
Under hypnosis, the "alters" (other personalities) may come out and reveal the abusive childhood memories. Although the most common use for hypnotherapy is for calming and soothing the person during their treatment.