Schizophrenia Causes and Risk Factors: Is It Genetic?

Some health conditions, like cancer or diabetes, can run in families. If a parent or grandparent has one of these conditions, you might wonder if you’re at higher risk. But what about schizophrenia? Can it be passed down through genes?

Schizophrenia is a serious and complex mental health condition. It affects how someone behaves and thinks, with symptoms like hearing voices or believing things that aren’t real. These symptoms can be scary and confusing, and they often leave people wondering why this is happening.

Scientists don’t yet know the exact cause of schizophrenia, but it’s clear that there’s no single reason. Schizophrenia likely results from a combination of genetic factors, environmental influences, and life experiences. In this article, we’ll explain what can raise a person’s risk and what that might mean for families.

The Genetics of Schizophrenia

Schizophrenia isn’t inherited the same way traits like eye color or curly hair are. Still, if a family member has schizophrenia, your risk is higher than that of someone with no family history.

Even if someone in your family has schizophrenia, that doesn’t mean that you’ll get it, too. Many people diagnosed with schizophrenia don’t have a family history of it. This shows that while genes play a role, they don’t tell the whole story. Other factors also matter, such as your environment during childhood and adolescence, brain development, and certain life experiences.

What Research Tells Us About Schizophrenia Genetic Risk

To understand genetic risk, researchers have studied families, twins, and adopted children. In the general population, about 1 in 100 people develop schizophrenia. If one parent has it, each child’s risk is about 10 percent to 15 percent. If both parents have schizophrenia, the risk can be as high as 35 percent to 46 percent.

Studies on twins help researchers better understand how much schizophrenia is linked to genes. Identical twins share the exact same genes — 100 percent of their DNA. If one twin has schizophrenia, the other one has about a 40 percent to 50 percent chance of also having it. That also means that about half of identical twins don’t get the illness, despite having the same genes — so other factors, such as environment or life circumstances, must also be involved.

Fraternal twins share only about half of their genes. If one twin has schizophrenia, the other has about a 1 in 8 chance of developing it. The more genes you share with someone who has schizophrenia, the higher your risk may be.

Adoption studies also support this idea. Children born to parents with schizophrenia but raised by people without it still had a higher chance of developing the condition. This suggests that the risk comes more from biology than parenting style or environment alone.

Other Types of Genetic Studies

Today, scientists use advanced tools to look at genes in large groups of people. One method, called genome-wide association studies (GWAS), looks for patterns in DNA. These studies have found many small changes in genes — called genetic variants — that can raise the risk of schizophrenia. These small changes don’t cause schizophrenia by themselves, but they may affect how neurons (brain cells) send messages using chemicals like dopamine and glutamate.

Environmental and Other Risk Factors for Schizophrenia

Even if someone has a genetic risk, their environment can also play a role. For example, stressful experiences — especially during childhood or adolescence — or birth complications may trigger the illness in someone who’s already vulnerable due to their genes.

Adolescent or Childhood Trauma

Scientists have found that early life stress can have lasting effects on the brain. When a child experiences trauma — such as neglect, bullying, or the loss of a parent — the brain’s stress system becomes overactive. This can change how the brain develops, especially in areas that control thinking and emotions. Stress during these early years can also affect how different brain regions grow and connect as a person reaches adulthood.

Substance Use

Using illicit drugs has been linked to a higher risk of schizophrenia or related conditions. Not everyone who uses substances will get schizophrenia, but the risk appears to be greater for those who start using drugs at a younger age or already have a genetic risk.

Pregnancy and Birth Complications

Certain problems during pregnancy or birth can also raise the risk of schizophrenia, including:

• Early birth
• Low birth weight
• Lack of oxygen at birth
• Exposure to high levels of stress during pregnancy

Some studies show that illness during pregnancy, such as the flu, may affect how the baby’s brain develops. One theory is that inflammation in the mother’s body could interfere with early brain growth and lead to long-term changes.

A complicated pregnancy or birth doesn’t mean a child will develop schizophrenia. However, when combined with genetic and environmental risk factors, it could raise the chances.

Additional Risk Factors

In addition to genetics and life experiences, a few other factors may raise the risk of schizophrenia.

The Time of Year You’re Born

People born in late winter or early spring have a slightly higher chance of developing schizophrenia. Scientists believe this may be due to a higher rate of infections, like the flu, during colder months of pregnancy. Vitamin D deficiency, which is also more common at this time of year, may also play a role.

Having an Older Father

Studies show that babies born to fathers over age 50 have a higher risk of schizophrenia. This may be because older parental age increases the chance of genetic mutations that may affect brain development.

Immune System Problems

Issues with the immune system may also be involved in schizophrenia risk. Some research suggests that an overactive immune system can change how brain cells work, possibly increasing the risk of psychotic disorders such as schizophrenia and bipolar disorder.

Certain autoimmune conditions may also raise the risk, including:

• Hemolytic anemia (low red blood cell counts)
• Celiac disease (an illness caused by an immune reaction to eating gluten)
• Interstitial cystitis (a chronic bladder condition)
• Thyrotoxicosis (an overactive thyroid)

Brain Abnormalities

Researchers have found that people with schizophrenia often show differences in brain structure. These changes may be present before symptoms of schizophrenia begin, sometimes even in the womb. One common change involves lower levels of gray matter — the part of the brain that helps with thinking, memory, and decision-making. The brain’s prefrontal and temporal lobes may be most vulnerable.

Speak With a Healthcare Professional

Schizophrenia is a complex condition with no single cause. Certain risk factors may raise your chances, but they don’t mean you’ll definitely develop schizophrenia. If you have concerns about your risk — or that of a loved one — talk with a mental health professional. Early support and understanding can make a big difference.

Talk With Others Who Understand

On MySchizophreniaTeam, the site for people with schizophrenia and their loved ones, people come together to ask questions, give advice, and share their tips with others who understand life with schizophrenia.

Have you or a family member been diagnosed with schizophrenia? Have you wondered whether genetics or other risk factors played a role? Share your thoughts in the comments below.