Many people believe, falsely, that having a 'split personality' is the same as schizophrenia. Well, it is not. There are in fact important differences.
The term schizophrenia is from Bleuler (1911), who firstly identified more and milder varieties of the disease. He spoke of a Gruppe der Schizophrenien (group of schizophrenics). Schizophrenia means 'split mind'... which goes some way to explaining the present confusion.
Schizophrenia is the label applied to a group of disorders characterized by severe personality disorganization, distortion of reality, and an inability to function in daily life1.
Typical symptoms of schizophrenia include hallucinations, mostly visual and auditory. To try to interpret these very realistic hallucinations, the sufferer develops delusions. A common delusion is that a schizophrenic may think he has a magic power or that he is God. This is a psychotic state. A psychosis affects the brain and damages it.
Disorders in emotional perception, movement (stiff movements, for example) and problems with speech (such as abruptly stopping in the middle of a sentence and starting another), may make the sufferer look bizarre to others.
The most common form is paranoid schizophrenia. This is where the sufferer's thoughts are controlled by strong suspicious delusions, and auditory hallucinations, such as 'hearing voices' which is very common. In comparison with other forms of schizophrenia, the disorders of emotional perception, movement and speech are rather small.
The development of schizophrenia often starts during adolescence or young adulthood. It is believed that it is caused by genetic defects triggered by stress factors like depression, the death of a dear person, or other experiences that are hard to cope with.
The prognosis of schizophrenia is bad when the disease has developed slowly; when there were no significant factors to trigger it; when it started to develop early; and when there are more family members suffering from schizophrenia. Treatment includes the taking of medications to suppress psychosis and joining psychotherapy. During non-psychotic episodes the sufferer has to learn to live with the symptoms and to avoid the possible triggers which prompt the psychosis; such as pressure, unstable and unhealthy lifestyle, stress and insecure feelings.
A split personality has nothing to do with schizophrenia, but more with Multiple Personality Syndrome (MPS). This is a psychiatric disorder that causes the sufferer's personality to divide into sub personalities, also known as alters. The alters have their own memory, and don't know of each other's existence. Consequently, the sufferer has episodes of amnesia.
The development of MPS is almost always triggered by severe abuse, including sexual abuse. During the traumatic experience the person becomes dissociated from the experience, becomes 'not there', and an alter personality takes over the pain. For every traumatic experience an alter is created. The alternating of the alters is easily recognized by the changing of the voice of the sufferer.
MPS is one of the most severe forms of defence mechanisms used to cope with extremely traumatic experiences.
Since 1994, MPS has been officially classified as Dissociative Identity Disorder in the DSM-IV2 as the alters are more identities, rather than personalities, based on dissociations.
As MPS (or DID) is believed to be very rare, not much research has been done. Therefore, not much is known of the prognosis. It is considered that the later the development of the alters takes place, the better. Another outcome of research is the belief that:
... after the age of 50, the alternating of the alters would spontaneously reduce3.
The experience gained by research is that sufferers who had re-integrated alters have a better recovery rate than sufferers with still divided alters. The integration of the alters is always accomplished by many years of intensive psychotherapy.
There are many differences between schizophrenia and 'split personality' (or MPS/DID). In practice this doesn't always show immediately. Careful observation of the sufferer and his or her symptoms over a long period is needed before a diagnosis can be reached. This is a normal practice in psychiatry; every person is different, and all the symptoms mentioned above can look different. It is almost unavoidable that a person will be mis-diagnosed at the start of treatment. As long as treatment fits the sufferer and the diagnosis is adjusted along the way, there isn't a problem. Although it is often hard to recognise what kind of disease a person is suffering from, the differences between schizophrenia and MPS are rather different.