Understanding Genetic Risks and Environmental Factors
Medically reviewed by Elle Markman, PsyD, MPH
Whether you love someone with the mental illness or have seen it depicted in movies and pop culture, you might find yourself wondering what causes schizophrenia. Unfortunately, scientists don’t know exactly what causes this mental illness. They do, however, understand that genetics plays a large role. For instance, if you have an immediate family member with schizophrenia, you’re 6 times more likely to experience the illness yourself, compared to people with no family history.
Environmental factors, including some that occur while in the womb, can also contribute to developing schizophrenia.
Continue reading to learn more about what causes and triggers schizophrenia.
What Causes Schizophrenia to Develop?
Most people who have schizophrenia first develop symptoms between the ages of 16 and 30. Researchers don’t know exactly what causes the illness, or why it emerges at those ages. However, they know that the illness has genetic, epigenetic (behavior and environment), and environmental causes.
There’s a strong genetic link to developing schizophrenia, which is why the disease often runs in families. About 80% of the chance of developing schizophrenia can be explained by genes. This is called heritability. It means that if you have a close relative with schizophrenia, like a parent or sibling, you’re 6 times more likely to have the condition yourself.
Scientists don’t believe there’s one gene that is responsible for schizophrenia. Instead, they think there are many genes at play. However, they don't have a full understand of what genes impact the risk for schizophrenia.
Epigenetics is the study of how behavior and environment impact how genes work. Scientists believe there are strong epigenetic risk factors that impact the development of schizophrenia. This explains why some people with a genetic risk for the disease develop symptoms, while other people with the same genes do not. Scientists haven’t yet identified why the way some genes are expressed can increase risk.
Some of the risk is explained by environmental factors; although scientists are still working to understand exactly why these factors increase risk.
Some research suggests that using drugs, particularly during the teen years, can increase risk for schizophrenia. However, people who are predisposed to schizophrenia may also be at a higher risk of developing substance use disorder. Drug use alone cannot trigger schizophrenia, and drug use during the teenage years cannot be blamed for causing the illness.
Scientists also believe that exposure to viruses, including while a fetus is in the womb, can increase risk for developing schizophrenia. However, they haven’t identified specific viral triggers of schizophrenia.
Schizophrenia in Identical Twins
Identical twins share 100% of their genes, so researchers often study them to determine how genetics influences disease progression. With schizophrenia, if one identical twin has the illness, the other has just a 50% chance of developing it.
This shows that while the genetic risk is strong, epigenetic and environmental factors play a large role in the development of the disease as well.
Schizophrenia Risk Factors
Genetics is the biggest risk factor for developing schizophrenia. However, many people with the disorder don’t have a known family history of the mental illness. In addition, many people who have close relatives with the disease don’t develop it themselves.
There are many risk factors that can contribute to schizophrenia, including:
Prenatal health, including lower vitamin D levels and exposure to viruses in the womb
Birth trauma, including being born prematurely or after a long, difficult delivery
Brain structure, including differently sized areas of the brain and different connections between brain areas than in healthy individuals
Substance use, particularly cannabis during the teenage years
Viral infections, especially before birth
Poverty and other socioeconomic factors
People who have schizophrenia experience episodes, or periods of more symptoms, often followed by periods of fewer symptoms. Sometimes these episodes happen for no obvious reason. Other times, the triggers for schizophrenia can include:
Stress: This can include housing insecurity, job stressors or loss, ending a relationship, abuse, and anything else that impacts stress levels.
Drug use: Drugs, including marijuana, cocaine, methamphetamine and LSD, can trigger an episode or relapse.
Causes of Relapsing Schizophrenia
There’s no cure for schizophrenia. Treatment involves managing symptoms, but most people with the condition will experience a relapse during their lifetime. Sometimes, a relapse of schizophrenia can be triggered by stress or drug use, but in other cases, there’s no clear cause—relapses are a typical part of this disease.
If you have schizophrenia, or love someone with the illness, it’s important to learn to recognize the early signs of relapse. When you notice changes to mood or functioning, seek help early. Adjusting medications and behaviors may help you avoid a full-fledged episode.
Scientists aren’t exactly sure what causes schizophrenia, but they know that genetics play an important role. That’s why the disease runs in families. However, there’s no one gene that causes the disorder. Instead, many genes interact with environmental factors and triggers, including substance use, viral infections, and stressors, to increase a person’s risk for schizophrenia.
If you or your loved one have this disease, remember that there’s no shame. Nothing you did caused the illness. Being an advocate, following your treatment plan, and understanding your disease can help you live well with schizophrenia.
Read the original article on Verywell Health.