Although the exact causes of schizophrenia are not known, it appears that several factors increase a person's risk for the illness. These factors interact with one another to influence the development and the course of schizophrenia (Strauss and Carpenter 1981; Weinberger and Hirsch 1995), and different factors assume importance at different stages in the individual's development. Genetic factors and complications of pregnancy and delivery can each play a part in forming the new-born infant's predisposition to developing the illness. The timing of the onset of illness in later life depends upon the extent of the person's vulnerability and exposure to a variety of stresses. Precipitating stresses may be biological in nature (e.g., hallucinogenic drug abuse) or social (e.g., losing a relative). These and other factors and stresses also affect the course and outcome of the illness.
     Although the exact causes of schizophrenia are not known, it appears that the interaction of a number of factors, including genetic factors, complications of pregnancy and delivery that may affect the developing brain, and biological and social stresses, play a role in the development of the illness.
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