It is generally agreed that schizophrenia is caused by a combination of factors rather than a single one.
Dopamine is one of the chemicals that carries messages between brain cells. There is evidence that too much dopamine may be involved in the development of schizophrenia, but it’s still not clear how, or whether everyone diagnosed with schizophrenia has too much dopamine.
Neuroleptic drugs (antipsychotics), which are sometimes used to treat schizophrenia, target the dopamine system (see 'Medication' in Treatments).
Stressful life events
Highly stressful or life-changing events may trigger schizophrenia. These include:
- social isolation
- being out of work
- living in poverty
- being homeless
- losing someone close to you
- being physically or verbally abused, or harassed.
Some people may develop symptoms of schizophrenia as a result of using cannabis or other street drugs such as cocaine and amphetamines.
If you already have schizophrenia, using street drugs can make the symptoms worse. Drinking alcohol and smoking may also limit how effectively medicines treat the symptoms of schizophrenia. (See our information on Understanding the mental health effects of street drugs).
Some families seem to be prone to schizophrenia, which suggests a genetic link. Rather than there being a specific gene for schizophrenia however, it is thought that certain genes might make some people more vulnerable to the condition.
Research is happening all the time into what might cause schizophrenia. For example there is evidence that physical differences in, or injury to the brain may be linked to schizophrenia, and that some of this process might happen before someone is born. Research into other possible causes, including viruses, hormonal activity (particularly in women), diet, allergic reaction or infection is ongoing.
Are some people more likely to be diagnosed than others?
About one in every hundred people is diagnosed with schizophrenia. It seems to affect roughly the same number of men and women. Most people diagnosed with schizophrenia are aged between 18 and 35, with men tending to be diagnosed at a slightly younger age than women. Some studies suggest that living in cities increases the risk of developing schizophrenia.
African-Caribbean men in the UK are much more likely to be diagnosed with schizophrenia than their white counterparts. This is despite no evidence that they are biologically more vulnerable to it. Suggestions have been made that this is caused by difficult life events, such as migration, racism, environment and cultural differences that affect mental health.
It may also be that psychiatrists with very different cultural, religious or social experiences to their patients mistakenly diagnose schizophrenia.