There have been many theories to try to explain schizophrenia. The cause is not known, but certain factors have been found to be different in people who develop schizophrenia. Some of the possible factors are outlined below.

• The brain structure of people with schizophrenia may be abnormal.
• Subtle blood flow changes in certain parts of the brain.
• Shortage of certain brain chemical receptor molecules in these parts of the brain.
• Enlarged lateral ventricles (the fluid-filled spaces in the brain).
• Abnormal nerve pathway connections in part of the brain.
• There is evidence that, in predisposed people, schizophrenia can be triggered by stressful experiences and possibly by some recreational drugs such as cannabis and cocaine.
• Studies suggest that it runs in families, but the risk of getting schizophrenia, if a family member has it, is still relatively small.