Multiple Personality Disorder

A person diagnosed with multiple personality disorder can have as many as a 100 or as few as two separate personalities. (About half of the recently reported cases have ten or fewer.) These different identities can resemble the main personality or they may be a different age, sex, race, or religion. Alters may resemble each other or be very unique. Each personality can have its own posture, set of gestures, and hairstyle, as well as a distinct way of dressing and talking. Some alters may speak in foreign languages or with an accent. Sometimes alternate personalities are not human, but are animals or imaginary creatures instead.

The process by which one of these personalities reveals itself and controls behavior is called switching. Most of the time the change is sudden and takes only seconds. Sometimes, however, it can take from hours or days. Switching is often triggered by something that happens in the patient's environment, but personalities can also come out under hypnosis or when the patient is given amyl nitrate ("truth serum").

Sometimes the most powerful personality serves as the gatekeeper and tells the other weaker personalities when they may reveal themselves. Other times personalities fight each other for control. Most patients with MPD experience long periods during which the host personality, also called the main or core personality, remains in charge. During these times, their lives may appear normal.

When an alter dominates, however, chaos often reigns. Ninety-eight percent of people with MPD have some degree of amnesia when an alternate personality surfaces. When the host personality takes charge once again, the time spent under control of the alter is completely lost to memory. In some cases of MPD the host personality may remember confusing bits and pieces of the past. In some cases alters are aware of each other, while in others they are not.

Because alternate personalities are formed by childhood disassociation as a result of trauma, it is not surprising that 86% of people with MPD have one alter with a child's personality. Childhood and adolescent alters handle and act out emotions the abused child could not, such as rage or terror. Some act in very negative ways, avenging and persecuting the host personality to be self-destructive. Other alters, called internal self helpers, watch what is going on and give advice. Sometimes people with MPD describe these alters as seeing everything and feeling nothing. Other alternate personalities, however, act as friends.

One of the most baffling mysteries of multiple personality disorder is how alternate personalities can sometimes show very different biological characteristics from the host and from each other. Several personalities sharing one body may have different heart rates, blood pressures, body temperatures, pain tolerances, and eyesight abilities. Different alters may have unique reactions to medications. Sometimes a healthy host can have alternate personalities with allergies and even asthma. An alter's blood glucose (sugar) may respond differently to insulin than the host's. Since studies done on people with such dramatically different alters have been small, no conclusions can be drawn and the puzzle remains to be solved.