Causes of Schizophrenia


It is difficult to identify the causes of schizophrenia, but research suggests that several physical, genetic, psychological and environmental factors interact and make people more likely to develop the condition. Current thinking is that some people may be prone to schizophrenia, but sometimes a stressful or emotional life event might trigger a psychotic episode. However, it is not known why some people develop symptoms while others do not.


There are some risk factors for schizophrenia that you cannot change. These include:


Schizophrenia tends to run in families, but no individual gene is responsible. It is more likely that different combinations of genes might make people more vulnerable to the condition. However, having these genes does not necessarily mean that you will develop schizophrenia.

Evidence that the disorder is partly inherited comes from studies of identical twins brought up separately. They were compared with non-identical twins raised separately, as well as with the general public. For identical twins raised separately, if one twin develops schizophrenia, the other twin has a one in two chance of developing it. In non-identical twins, who share only half of each other's genetic make-up, when one twin develops schizophrenia, the other twin has a one in seven chance of developing the condition.

While this is higher than in the general population (where the chance is about one in a 100), it suggests that genes are not the only factor influencing the development of schizophrenia.


Brain development

Many studies of people with schizophrenia have shown that there are subtle differences in the structure of their brains or small changes in the distribution or number of brain cells. These changes are not seen in everyone with schizophrenia and they can occur in people who do not have a mental illness, but they suggest that schizophrenia may partly be a disorder of the brain.



These are the chemicals that carry messages between brain cells. There is a connection between neurotransmitters and schizophrenia because drugs that alter the levels of neurotransmitters in the brain are known to relieve some of the symptoms of schizophrenia. Research suggests that schizophrenia may be caused by a change in the level of two neurotransmitters, dopamine and serotonin. Some studies indicate that an imbalance between the two may be the basis of the problem. Others have found that a change in the body’s sensitivity to the neurotransmitters is part of the cause of schizophrenia.



There is some evidence from research that certain viral infections, including the polio virus and the flu virus, may play a role in the development of schizophrenia.


Pregnancy and birth complications

Although the effect of pregnancy and birth complications is very small, research has shown that the following conditions may make a person more likely to develop schizophrenia in later life:

  • bleeding during pregnancy, gestational diabetes or pre-eclampsia
  • abnormal growth of a baby while in the womb, including low birth weight or reduced head circumference
  • exposure to a virus while in the womb
  • complications during birth, such as a lack of oxygen (asphyxia) and emergency caesarean section


Head injury

Traumatic head injury, such as the kind sustained in a fall or a traffic accident, may make people more likely to develop schizophrenia, but it is not known why this happens. Research has also suggested that head injuries during childhood could lead to the development of schizophrenia in people who are already prone to it.



There are some known triggers for schizophrenia.

  • Stress: the main psychological triggers of schizophrenia are stressful life events, such as bereavement, losing your job or home, a divorce or the end of a relationship, or physical, sexual, emotional or racial abuse. These kinds of experiences, though stressful, do not cause schizophrenia, but can trigger its development in someone who is already vulnerable to it.
  •  Drug abuse: drugs do not directly cause schizophrenia, but studies have shown that drug misuse increases the risk of developing schizophrenia or a similar illness. Certain drugs, particularly cannabis, cocaine, LSD or amphetamines, may trigger some of the symptoms of schizophrenia, especially in people who are susceptible. Using amphetamines or cocaine can lead to psychosis and can cause a relapse in people who are recovering from an earlier episode. Three major studies have shown that teenagers under 15 who use cannabis regularly, especially ‘skunk’ and other more potent forms of the drug, are up to four times more likely to develop schizophrenia by the age of 26.


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"There can be life after schizophrenia: in my own case, nearly thirty years of a very satisfying and rewarding, though not always easy, existence."


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