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The course of schizophrenia
Wide variation occurs in the course of schizophrenia. In some cases the onset of illness is gradual, extending over the course of months or years; in others it can begin suddenly, within hours or days. Some people have episodes of illness lasting weeks or months with full remission of symptoms between each episode; others have a fluctuating course in which symptoms are continuous; others again have very little variation in their symptoms of illness over the course of years. The final outcome from the illness in late life can be complete recovery, a mild level of disturbance or continued severe illness.
Figure I.2 is an illustration of the onset, course and outcome of the illness in 228 people with schizophrenia followed into old age by the Swiss psychiatrist, Luc Ciompi. He found that the onset of the illness was either acute (with less than six months from first symptoms to full-blown psychosis) or, conversely, insidious, in roughly equal numbers of cases. Similarly, the course of the condition was episodic or continuous in approximately equal numbers of patients; and the outcome was moderate to severe disability in half the cases and mild disability or full recovery in the other half. Full recovery was observed in more than a quarter of the patients. It is clear that the course of schizophrenia varies a good deal between individuals and that the outcome is often favorable.
It is also true to say that schizophrenia usually becomes less severe as the person with the illness grows older. In addition, the later the illness begins in life, the milder it proves to be. Women usually develop their first symptoms of schizophrenia later than men and the course of their illness tends to be less severe. Onset of schizophrenia before the age of 14 is rare, but when it does begin this early it is associated with a severe course of illness. Onset after the age of 40 is also rare, and is associated with a milder course.
What Causes Schizophrenia?
There is no single organic defect or infectious agent which causes schizophrenia, but a variety of factors increase the risk of getting the illness—among them, genetics and obstetric complications.
Relatives of people with schizophrenia have a greater risk of developing the illness, the risk being progressively higher among those who are more genetically similar to the person with schizophrenia (see Figure I.3). For a nephew or aunt the lifetime risk is about two percent (twice the risk for someone in the general population); for a sibling, parent, or child the risk is about ten percent, and for an identical twin (genetically identical to the person with schizophrenia) the risk is close to 50 percent.
Studies of people adopted in infancy reveal that the increased risk of schizophrenia among the relatives of people with the illness is due to inheritance rather than environment. The children of people with schizophrenia have the same increased prevalence of the illness whether they are raised by their biological parent with schizophrenia or by adoptive parents.
There is evidence implicating several genes in causing schizophrenia, and it is likely that more than one is responsible, either through an interactive effect or by producing different variants of the disorder.
Since identical twins only have a 50 percent risk of developing the illness, we know that genetics alone do not explain why someone gets the illness. Other powerful factors have to play a part; one of these is problems of pregnancy and delivery. The risk for people born with obstetric complications, such as prolonged labor, is double the risk for those born with none. A history of obstetric complications has been found in up to 40 percent of patients with schizophrenia, making it a major risk factor.
The risk of intrauterine brain damage is increased if a pregnant woman contracts a viral illness. We know that more people with schizophrenia are born in the late winter or spring than at other times of year, and that this birth bulge sometimes increases after epidemics of viral illnesses like influenza, measles and chickenpox. Maternal viral infections, however, probably account for only a small part of the increased risk for schizophrenia.