Sometimes, the disease is assymetrical, which means that what one personality knows, the others inherently know. The patient has at least two distinct identities or personality states. Each of these has its own, relatively lasting pattern of sensing, thinking about and relating to self and environment. At least two of these personalities repeatedly assume control of the patient's behavior. Common forgetfulness cannot explain the patient's extensive inability to remember important personal information.
Some disorders have similar or even the same symptoms.
This ability may be used and is extremely effective defense against acute physical and emotional pain, or anxious anticipation of that pain. By this dissociative process, thoughts, feelings, memories, and perceptions of the traumatic experiences can be separated off psychologically, allowing the patient to function as if the trauma had not occurred. Often, even after the traumatic circumstances are long past, the left-over pattern of defensive dissociation remains. Chronic defensive dissociation may lead to serious dysfunction in work, social, and daily activities. Repeated dissociation may result in a series of separate entities, or mental states, which may eventually take on identities of their own.