Causes of schizophrenia

The causes of schizophrenia are unknown, but like with many mental health conditions, it is usually a combination of the following factors rather than having a primary cause:

• Psychological causes and brain chemistry
• Brain structure
• Genetics
• Complications at birth
• Life experiences, such as trauma and stress

Is schizophrenia genetic?

Scientists believe there is a hereditary or genetic component to schizophrenia, meaning that it does often run in families, but it does not necessarily mean you will develop schizophrenia if a member of your family has schizophrenia, such as your mother or father. Also, no single gene is thought to be responsible for schizophrenia. It may be a combination of genes that increases your risk of developing schizophrenia.

We partially know about the genetic component to schizophrenia due to studies on identical and non-identical twins. If one identical twin has schizophrenia, there is a 1 in 2 chance of the other twin developing it too. This is even the case if they were raised apart and had different life experiences. In non-identical twins, this decreases to a 1 in 8 chance for the other twin to develop schizophrenia. This is because of their non-identical genetic makeup. These rates are significantly higher than the general population, who have a 1 in 100 average risk of schizophrenia.

Does brain structure contribute to schizophrenia?

Some people with schizophrenia have subtle changes in their brain structure, meaning that schizophrenia may partly be a brain disorder. However, these changes in brain structure are also sometimes present in people without schizophrenia. Similarly, brain chemistry may play a part in schizophrenia, like it does in other mental health conditions. An imbalance of some brain chemicals (neurotransmitters), like dopamine and serotonin, may be partially responsible.

Is there a link between schizophrenia and pregnancy?

There may be a link between pregnancy or birth complications and schizophrenia. People who develop schizophrenia are more likely to have experienced birth complications such as premature birth, low birth weight, lack of oxygen during birth (asphyxia). Studies have also shown that smoking during pregnancy also increases the risk of the child developing schizophrenia.

What triggers schizophrenia in people who are at risk?

A number of life events or experiences, such as childhood trauma, can trigger schizophrenia in people who are vulnerable to developing it, but they do not cause the illness to develop. These can include:

• Bereavement
• Physical, sexual, or emotional abuse
• Childhood trauma
• Divorce, or the end of a relationship
• Losing a job or home
• Moving to a new city or country
• Extreme stress

Studies also show that substance use or drug abuse might increase your risk of developing schizophrenia, psychosis, or similar experiences. This includes:

• Cannabis, particularly strong cannabis
• Cocaine
• LSD
• Amphetamines

Studies show that teens and young adults who regularly use cannabis are more likely to develop schizophrenia later in life. However, it’s not clear if drugs cause these symptoms to develop, or if people at risk of schizophrenia and who have had difficult life experiences are more likely to use drugs.

In people who have had previous experiences of psychosis or have had previous acute episodes of schizophrenia, alcohol and drug use can also cause a relapse or affect recovery.