The cause of schizophrenia is not yet known, and research into it is happening all the time. But it is generally agreed that schizophrenia is caused by a combination of factors rather than a single one.
This page has information about possible causes of schizophrenia.
Stressful life events
Highly stressful or life-changing events may sometimes trigger schizophrenia. These can include:
The onset of schizophrenia for me was sudden and dramatic, though it followed a period of depression and acute stress. A really compelling and powerful voice started to try to control me.
Cannabis and other recreational drugs
Some people may develop symptoms of schizophrenia after using cannabis or other recreational drugs. Researchers still aren't sure whether using recreational drugs directly causes schizophrenia, or if people who develop schizophrenia are also more likely to use recreational drugs.
If you already have schizophrenia, research has shown that using recreational drugs may make the symptoms worse. Some studies suggest that people who use high-potency cannabis ('skunk') during a period of recovery are more likely to have a relapse of their symptoms.
Drinking alcohol and smoking may also stop medication from effectively treating your symptoms. (See our information on recreational drugs and alcohol.)
Does schizophrenia run in families?
You are more likely to develop psychosis such as schizophrenia if you have a parent or sibling who has experienced psychosis, but researchers aren't sure why this happens.
It is thought that certain genes might make some people more vulnerable to developing schizophrenia, which could explain why people in the same family may be affected.
Some possible causes of schizophrenia are also more likely to affect people living in the same household. For example, some studies suggest that living in cities increases the risk of developing schizophrenia – but researchers don't yet know why.
Chemicals in the brain
Some chemicals seem to behave differently in the brains of people who experience schizophrenia. These chemicals are thought to include dopamine, which helps to carry messages between brain cells.
One theory is that people with schizophrenia have more dopamine in their brains, or that dopamine has different effects for them. Some research suggests that other chemicals are involved too.
Antipsychotics, which are sometimes used to treat schizophrenia, can help to lower dopamine levels. (See our information on antipsychotics.)
More recently my physical health has deteriorated... I have become more agoraphobic and find group settings harder than before.
Other possible causes of schizophrenia
Some studies suggest that physical differences in the brain, or injury to the brain, may be linked to schizophrenia. Other physical causes have also been suggested.
Research into a wide range of other possible causes is ongoing.
Are some people more likely to be diagnosed than others?
About one in every 100 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.
African-Caribbean men in the UK are particularly likely to be diagnosed with schizophrenia, despite there being no evidence that they are biologically more vulnerable to it. It has been suggested 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.
This information was published in February 2017. We will revise it in 2020.