Multiple Personality Disorder (MPD) is one of the most fascinating types of mental disorder. It is an extreme dissociative disorder - a psychiatric condition marked by great disturbances in memory and identity.
The MPD sufferer displays two or more contrasting (alter) personalities that exchange control over his/her behaviour.
Recent research suggests that the normal person has layers of different ways of being that are integrated into a whole during development. If this development is traumatically disrupted, abnormal layers of the self are developed and dramatically revealed.
It is well established that a person can experience different mental states, daydreams, sleep, dreams, catatonia, etc., in addition to MPD. MPD was explained in past centuries as possession by evil spirits. When it was discovered that certain functions are localised in the right or left side of the brain, it became popular to describe MPD as a short-circuiting between the two sides of the brain, although this approach has produced few clear-cut results.
It is now clear that childhood trauma is the root cause of the condition. Severe incestuous sexual abuse is a very common trauma connected with MPD, which helps explain why most reported cases of MPD are female. Other forms of trauma can also precipitate MPD, e.g. torture, or witnessing the murder of family members.
Confronting such terrible circumstances produces an extreme response in the child. Some children create and internalise imaginary companions - angels, animals, heroes - and repeatedly escape from traumatic reality by living in these alter personalities. Over time, each alter personality acquires a specific sense of self, and a set of behaviours and biographical details.
Eventually the alter personalities share out control over the person's behaviour. a particular personality will probably be aware of some of the other alter personalities, but be blind to the rest.
Every MPD sufferer has at least one host personality that dominates most of the time. This personality is typically anxious, scrupulous, depressed and overwhelmed by life. The host personality is often either unaware of the other personalities or denies their existence when presented with evidence. The person's original personality, that existed before the trauma, is almost always different from the host personality.
The range of alter personalities in a subject is often a balance of darker types offset by positive helper personality types. It is common for an MPD patient to have a persecutor personality that attempts to hurt or kill the host (or another) personality. A promiscuous alter personality that indulges forbidden impulses is quite common. Prostitute alter personalities are common in female MPD cases. The compensatory helper personality in female MPD cases is often male. The personalities dress to suit their gender and can be sexually active, with either heterosexual or homosexual orientations.
The extent of the changes in the MPD subject accompanying the movement from one alter personality to another is amazing and raises fundamental questions about human potential. Dramatic physical changes can occur - pattern of facial wrinkling, posture and motor skills. Small slight women can have male protector personalities that are physically powerful. Some alter personalities can be especially gifted artistically or athletically. Another alter personality may suffer from a psychogenic disability, such as blindness or deafness.
Recent research on discrete mental states in newborn infants sheds much light on MPD. Complex behaviour, even in newborns, is made up of sequences and cycles of discrete states. Using physiological and behavioural measures, Peter Wolff of Boston's Children's Hospital describes five discrete states. State one is regular quiet sleep; state two is restless sleep; state three is alert inactivity; state four is "fussy"; state five is crying. Any of these states is active only for a limited time.
Even at the most fundamental level (newborn), a normal person is fluid and layered and changes in response to outside stimuli (startle a baby in state one and you have state five in a couple of seconds). As the child matures, additional discrete behavioural states arise in response to life experience.
In a normally integrated adult, switches between discrete states are usually imperceptible. An exception is the fight or flight response that immediately switches in when a person is confronted with a sudden danger, and prepares the body to immediately fight or flee the danger. Another benign example of dissociated behaviour is day-dreaming, escape from a boring situation into a more comfortable state of consciousness. In these cases dissociative behaviour is vital, or at least helpful.
However, under severe trauma the tactic of dissociation can lead to disorder. When a vulnerable young life is made to face unremitting abuse during a crucial developmental period, new abnormal discrete states are created, and the person becomes layered into several or many parts.
The passage from one to another, so fluid in a normal individual, becomes jarring and it seems as if one person has become several different people. The seeds of multiple personality are in everyone but they crystallise out only under severe trauma experienced at a critical stage of development.
William Reville is a senior lecturer in biochemistry at UCC.
