Schizophrenia tends to run in families, but genetics is not the only factor that can contribute to the development of the condition.

Schizophrenia is a complex psychiatric condition that can affect a person’s way of thinking, sense of self, and perceptions of the outside world. It can also lead to disorganized thoughts and difficulty concentrating or regulating emotions, which can affect school and work life and relationships.

The exact cause of schizophrenia is unknown, but many factors may play a role. Among these, experts have found genetics to be one of the strongest predictors of whether a person will develop schizophrenia.

This article examines the link between genetics and schizophrenia. It explores what this relationship means for family members of people with schizophrenia, what genetics can tell us about this condition, and how people can treat it.

Schizophrenia tends to run in families — that is, people are more likely to develop the condition if they have a family member who also has it.

But not everyone who has a close relative with schizophrenia will also have it. Many people with a family member with schizophrenia will not develop the condition themselves. Research suggests that if a parent has schizophrenia, the risk of passing it to their child is 13%. The risk jumps to more than 20% if both parents have the condition.

Twin studies also suggest that the relationship between genetics and the risk of schizophrenia is complicated. These studies include identical twins, who share nearly all the same genetic markers, to understand how people can pass down conditions such as schizophrenia through families.

A 2017 study including Danish twins showed that genetics are a strong predictor of the heritability of schizophrenia. But they are not the only predictor.

In the study, only 33% of people with an identical twin who had schizophrenia developed the condition themselves. The rate was lower for nonidentical twins, commonly known as fraternal twins. In these pairs, 7% of people with an affected twin also developed schizophrenia.

Additionally, a study from 2012 showed that 50% of the schizophrenia cases examined could have occurred due to new, or de novo, mutations that a person inherited from a family member.

Many experts believe that certain genetic mutations alter the physical and chemical makeup of the brain, making it more likely that schizophrenia will develop. Many of the genes experts have linked to schizophrenia affect processes in the brain related to the function of neurons, including growth and signaling.

These changes might make it harder for the brain to respond and adapt to other factors that may contribute to the development of schizophrenia. External factors that can influence the likelihood of developing schizophrenia include:

  • viral or parasitic infections, especially in the womb or during early childhood
  • complications before or during birth
  • stress or trauma
  • drug misuse

Family members may experience the same exposures, such as stress or trauma, or birth complications in the case of twins, which might contribute to the heritability of schizophrenia. In many cases, though, people can experience these exposures differently, even in the same family.

So, while genetics may affect the way the brain responds to external stressors, it does not guarantee that schizophrenia will develop. A person likely needs to experience other factors that may lead them to develop the condition.

Experts have not found a single gene that is solely responsible for the development of schizophrenia. Instead, some think that many genes play a role in changing the brain’s architecture, making schizophrenia more likely to develop.

As mentioned above, most of these genes linked to schizophrenia affect neurons in the brain. In many cases, these genes code for proteins in the synapse — the space between neurons. Many of these proteins are receptors or other molecules responsible for receiving and transmitting signals throughout the brain.

One 2022 study found that 50% of genes experts have linked to schizophrenia are also linked to brain morphology, meaning that the brain structure is affected.

Other genes linked to schizophrenia affect immune responses, but mutations in these genes appear to be more likely to influence schizophrenia risk in European populations than in other groups, including people of East Asian and African descent.

Schizophrenia has historically been a condition that is difficult to treat. The brain is a complicated organ, and without a good understanding of what causes schizophrenia, developing medications that help correct the symptoms has been challenging.

By studying the genes linked with schizophrenia, experts can better understand what processes in the brain are dysregulated. They can then try to develop new medications that work by correcting these processes, helping to improve brain function.

Many schizophrenia researchers are already working to use genetics to identify potential drug targets. Using sophisticated network analyses, some are even trying to find existing medications that experts can repurpose to help treat schizophrenia and other psychiatric conditions based on the genes involved.

In the future, as more medications are available, some experts are hopeful that they can personalize schizophrenia treatment based on a person’s individual genetic profile.

Genetics are a strong predictor of the likelihood of developing schizophrenia, but they are not the only one. Certain genetic mutations can affect the way the brain works, making it more susceptible to other factors that may lead to the development of schizophrenia. As a result, not everyone who is genetically at risk of schizophrenia will develop the condition.

As researchers learn more about the genes linked to schizophrenia, a better understanding of the condition and potential treatment targets is emerging. In the future, this may help support a more personalized approach to schizophrenia care.