Schizophrenia Causes: Genetics, Environment, and More

Medically Reviewed by Zilpah Sheikh, MD on April 20, 2024
5 min read

Doctors don’t know for sure what causes schizophrenia. Research shows a combination of genetics and your environment can trigger the disease. If you have a family member with schizophrenia, you're more likely to have it. Things like stressful life events, exposure to viruses or toxins before you were born, and trauma in your early childhood can also increase your risk. Scientists have also found changes in brain chemistry and structure when someone has schizophrenia.

Scientists have found that changes in the structure and chemical makeup of your brain may play a role in schizophrenia.

Brain structure in schizophrenia

If you have schizophrenia, you might have:

  • Larger spaces called ventricles in the brain
  • Smaller medial temporal lobes – the parts of the brain in charge of memory
  • Abnormal connections between brain cells

Studies have also linked schizophrenia with a loss of brain tissue. Positron emission tomography (PET) and magnetic resonance imaging (MRI) scans show that gray matter – the part of the brain that contains nerve cells – shrinks over time. Loss of brain tissue may be related to your symptoms of the illness.

Brain chemicals

You might also have differences in brain chemicals called neurotransmitters. These chemicals help brain cells “talk to” one another. Certain neurotransmitters may be too active or not active enough.

Dopamine and glutamate are neurotransmitters linked to schizophrenia. They carry messages that help you think and understand, and that motivate you. An imbalance of these chemicals could affect how your brain reacts to the world around you. That could lead to schizophrenia symptoms like hallucinations, where you see or hear things that aren’t real.

Dopamine has been linked to addiction. It also plays a role in other mental health and movement disorders, like Parkinson’s disease. One theory is that an imbalance of dopamine leads to symptoms like hallucinations and delusions. Antipsychotic drugs that treat schizophrenia block dopamine.

Glutamate is involved with memory, mood, and thinking, and it activates some parts of the brain. Your brain may have changes in glutamate activity. These changes could cause schizophrenia symptoms like a lack of emotion and poor social skills.

Doctors are trying to learn how brain circuits that use these chemicals work together or are related to each other.

Your genes are like a blueprint for your body. A change to these plans might increase your chance of getting diseases like schizophrenia. Research shows that almost 80% of the risk for schizophrenia lies in genes.

You’re more likely to get schizophrenia if someone in your family has it. If it’s a parent, brother, or sister, your chances go up by 10%. If your identical twin has it, your risk goes up by as much as 50%.

But some people with schizophrenia have no history of it in their family. Scientists think that in these cases, genes may have changed in that person to make the condition more likely.

Genes that cause schizophrenia

Doctors don’t think there’s just one “schizophrenia gene.” Instead, they believe it takes many genetic changes, or mutations, to increase your risk of having this mental illness. Usually, several small changes add up to a higher risk. 

Doctors aren’t sure how genetic changes lead to schizophrenia, or exactly which genes are involved. Some of the genes linked to schizophrenia affect brain development. Others are related to the immune system and inflammation. Inflammation is a response by your immune system to stressors, and it's been linked to the development of many physical and mental diseases. 

The default mode network (DMN) includes areas of your brain that are active when you’re at rest – daydreaming, reflecting, and processing thoughts and memories. If you have schizophrenia, you might have abnormal connections in this network that can cause issues with self-awareness, hallucinations, and delusions. The DMN may not turn off as usual when you're doing tasks, as it does in people without the illness. This might cause you to have trouble controlling your intrusive thoughts. Research shows that childhood trauma can have a negative effect on DMN function, which might cause schizophrenia later in life.



Things in your environment can also cause schizophrenia. Some of these are:

Problems during pregnancy and birth. You could be at higher risk if your mother had bleeding or high blood pressure during her pregnancy, or if she had an emergency cesarean section. Being born at a lower-than-normal weight increases the risk of getting schizophrenia at an earlier age. Exposure to a virus like the flu or herpes in the womb might also be a factor.

Traumatic life events. Sexual abuse, physical abuse, emotional abuse, bullying, or the death of a parent in childhood might increase your risk of having schizophrenia as an adult. There is a three times higher risk of having one of these life events within 3 years before schizophrenia symptoms start.

Substance use. Stimulant drugs like amphetamines and cocaine can cause psychosis. Some research shows that people who use cannabis have a two to three times higher risk of schizophrenia. The younger you start using these substances and the more often you use them, the more likely you are to have symptoms of psychosis.

Moving to a new country. People who are refugees from another country have a higher risk of schizophrenia. The problem could be from trauma they face along the way, such as discrimination and not having a home. The children and grandchildren of people who migrate to another country are also at risk.

You might have differences in your brain structure and chemicals called neurotransmitters if you have schizophrenia. Most of your risk comes from genes, but your environment may also play a role in causing this mental health condition. Problems when you were in the womb or being born, traumatic life events, and substance use might all be involved.

Can people with schizophrenia live normal lives?

Yes. Schizophrenia requires lifelong treatment with antipsychotic medicines and therapy. But with these treatments, you can go to school, have a job, and have healthy relationships.

What happens if schizophrenia is left untreated?

If you don’t treat schizophrenia, it can lead to psychotic symptoms like hallucinations and delusions. These symptoms may be frightening and can disrupt your life.

How does schizophrenia start off?

Changes in your genes make you more likely to get schizophrenia. Then something in your environment, like trauma or substance use, sets the condition in motion. Mood swings, a lack of focus, and social isolation may be the first signs of schizophrenia.

Does schizophrenia come and go?

In some people, schizophrenia symptoms come and go. Others have more consistent symptoms.