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Causes - Schizophrenia

The exact causes of schizophrenia are unknown.

A mix of factors can make a person more likely to develop the condition.

These include:

  • physical factors
  • genetic factors
  • psychological factors
  • environmental factors

You may be prone to schizophrenia. A stressful or emotional life event might trigger a psychotic episode. But it's not known why some people develop symptoms and others do not.

Increased risk

There are a number of things that increase the chances of schizophrenia developing.


You may be more at risk of developing schizophrenia if other people in your family have the condition.

It does not mean you will develop schizophrenia. There are other things that may influence the development of schizophrenia.

Brain development

There are some differences in the structure of the brain for people with schizophrenia.

These changes are not seen in everyone with schizophrenia. They can happen in people who do not have a mental illness. But they suggest schizophrenia may partly be a disorder of the brain.


Neurotransmitters are chemicals that carry messages between brain cells.

There's a link between neurotransmitters and schizophrenia. Drugs that change the levels of neurotransmitters can relieve some of the symptoms.

Pregnancy and birth complications

If you have schizophrenia, you are more likely to have experienced complications before and during birth.

For example:

  • a low birth weight
  • premature labour
  • a lack of oxygen (asphyxia) during birth

It may be that these things have a subtle effect on brain development.

History of traumatic events

Early traumas in life increase the risk of psychosis.

These include:

  • child sexual abuse
  • physical abuse
  • bullying

But not everyone who has had early trauma will develop psychosis. Also, not everyone who has psychotic experiences has experienced childhood abuse.


Triggers are things that can cause schizophrenia to develop in people who are at risk.


The main psychological triggers of schizophrenia are stressful life events, such as:

  • bereavement
  • losing your job or home
  • divorce
  • the end of a relationship
  • physical, sexual or emotional abuse

These kinds of experiences do not cause schizophrenia. But they can trigger its development in someone who is already vulnerable to it.

Drug abuse

Drugs do not directly cause schizophrenia. But drug misuse increases the risk of developing schizophrenia, or a similar illness.

Certain drugs may trigger symptoms of schizophrenia in people who are vulnerable.

For example:

  • cannabis
  • cocaine
  • LSD
  • amphetamines

Using amphetamines or cocaine can lead to psychosis. This can cause a relapse (setback) in people recovering from an earlier episode.

People under 15 who use cannabis regularly are up to 4 times more likely to develop schizophrenia by the age of 26. This is especially true for 'skunk' and other more potent forms of the drug.

Content supplied by the NHS and adapted for Ireland by the HSE

Page last reviewed: 1 September 2022
Next review due: 1 September 2025