Biological/Environmental Factors

Biological/environmental factors that may increase the risk of developing schizophrenia include complications during gestation or birth and viral infections. In addition, researchers have identified a number of areas of the brain where pathophysiologic processes linked to schizophrenia may occur.

Gestational and Birth Complications

People with schizophrenia have an increased prevalence of gestational and birth complications. However, the reason for this increased risk — and the degree to which it may be independent of genetic risk factors is unknown. Evidence for the possible role of such complications includes findings of an increased risk of schizophrenia :

• in the offspring of women who were in their 6th or 7th month of pregnancy during an influenza epidemic (suggesting that injuries during key periods of fetal brain development may play a role)
• following gestational or birth complications that caused a diminished supply of oxygen to developing brain regions.

Viral Infections

Although people have speculated for years that viral infections may play a role in schizophrenia, the evidence so far is only suggestive. Nevertheless, viral infections remain a plausible factor, especially those that alter genetic material, affect a person’s immune system, or influence a mother during gestation.

Psychosocial Factors

In the mid-20th century, many clinicians believed that psychosocial factors (the influence of family and society on a person) could cause schizophrenia. However, it is now generally believed that such factors are more likely to influence the time of onset and course of schizophrenia rather than to actually cause it.

Three theories regarding psychosocial factors and how they may influence the development of schizophrenia are summarized below. Keep in mind that some of the views underlying these theories are no longer considered credible.

• Psychoanalytic theories suggest that mental illness results from arrested childhood development. For example, Sigmund Freud postulated that an underdeveloped ego (sense of self) influenced the development of schizophrenia and that certain factors could make a person’s ego regress to a childlike or primitive state.
• Psychodynamic theories explain the development of schizophrenia in terms of how people respond internally to the outside world. For example, they state that schizophrenia could be a regressive response to overwhelming conflict with others, causing a distorted perception of the world.
• Learning theories postulate that people develop schizophrenia as a result of irrational reactions, thinking, and perceptions learned during childhood. For example, such theories postulate that children may develop symptoms after imitating parents who had significant emotional problems.