Schizophrenia is a mental illness that may be a group of conditions, rather than a single disorder. It has a large variety of symptoms, which can seem very different in one person from another. Schizophrenia causes someone to have an altered experience of reality and it affects people's thoughts, perceptions and behaviour.

It's thought that schizophrenia is caused by complex changes in brain functioning but the causes are not yet fully understood. There is no single cause - the condition usually develops in people who have a combination of genetic and environmental risk factors.

Genetics

Genes are the most important risk factor for schizophrenia. People with a parent or sibling with schizophrenia have a 10 per cent chance of developing it, whereas in the general population just 1 per cent have a chance of developing it. There is no single gene involved; rather, a number of genes may combine to increase the risk.

Environmental factors

Even where there is a genetic risk, most people do not develop schizophrenia. It can, however, be triggered by other issues such as:

• Pregnancy and birth factors: malnutrition, serious infections in pregnancy or birth complications can increase the risk of a child developing schizophrenia later in life.
• Drug abuse: in particular, the use of cannabis, amphetamines or hallucinogens.
• Trauma and stress: people who have experienced violence, traumatic events or severe stress have a higher risk of developing schizophrenia.
• Place or season of birth or family income can also influence the risk.

See a doctor if you or someone you know seems to be experiencing any of these symptoms.

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