Genetic predisposition plays a major role in developing schizophrenia. But research suggests it’s more complicated than just inheriting schizophrenia if it runs in your family.

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Researchers have long recognized that schizophrenia runs in families, suggesting a genetic component to developing this mental health condition.

But does having a genetic component mean you are at high risk of developing schizophrenia? Do other environmental, biological, or behavioral factors play a role?

The role genetics play in the development of schizophrenia interacts with other potential risks that can trigger it, such as family environment, pregnancy complications, and childhood trauma.

Genetic factors are believed to play a significant role in the development of schizophrenia. About 20 million people worldwide have this mental health condition.

However, the field of genetics is very complicated. Even large-scale genome studies can sometimes leave researchers with more questions than answers.

Schizophrenia is not consistently passed on from one generation to the next. Rather, it’s the result of a complex interplay of genetic, biological, and environmental factors.

Still, there’s no doubt about the importance of genes with schizophrenia.

While research estimates the lifetime risk of schizophrenia is about 1% in the general population, this risk increases to about 6.5% in people who have first-degree relatives — like a parent or sibling — with the condition.

The odds increase to more than 40% if you have an identical twin with schizophrenia.

But even if you have a parent or a sibling with schizophrenia, it doesn’t necessarily mean you will develop it, even when all the factors seem to line up.

In fact, most people with a close relative with schizophrenia do not develop it.

There’s no single “schizophrenia gene.” Rather, many genes and gene variants are linked to the condition.

There are also complex processes known as:

  • “de novo variants” (first-time genetic alterations)
  • “copy number variants” (when the number of copies of a particular gene varies from one person to the next)
  • various “loci” (locations in the human genome) that harbor common risk variants

In fact, some research suggests schizophrenia may not even be one disease, but rather a spectrum condition of eight distinct disorders, each with its own set of symptoms.

Different gene clusters cause different schizophrenia symptoms

In a large genome-wide study of more than 4,000 people with schizophrenia, researchers found distinct gene clusters that contribute to eight different “types” of schizophrenia.

According to this study, even various mutations within a single gene can lead to strikingly different symptoms among people.

Schizophrenia symptoms are typically divided into three distinct categories:

  • Positive symptoms: hallucinations and delusions
  • Negative symptoms: lack of motivation, inability to feel pleasure, absence of emotional expression
  • Cognitive symptoms: difficulties with concentration, memory, and attention leading to significant disability

Each person with schizophrenia can have a very different mix of all three of these symptom groups.

Even though genetic and environmental factors are often present in early life, schizophrenia symptoms typically do not begin to show prominently until young adulthood.

Schizophrenia can occur at any age, but the average age of onset for men is late teens to early 20s. In women, symptoms generally appear in their late 20s to early 30s.

Schizophrenia appears to share genetic overlap with other common mental health conditions. Close relatives of people with schizophrenia may be at a higher genetic risk of developing bipolar disorder, epilepsy, and autism.

In one major 2018 study, an international research team looked at the data of more than 33,000 people with schizophrenia, 20,000 people with bipolar disorder, and 54,000 people without either condition.

Researchers found 114 specific loci (locations in the human genome) that contribute to the risk of both schizophrenia and bipolar disorder. They also found four genome regions that distinguish the biological differences between the two conditions.

According to the study, it may be possible to determine whether a person is likely to develop certain symptoms of schizophrenia based on their individual genetic risk score for either condition.

For example, the study found that people with bipolar disorder with psychosis are likely to have a higher genetic risk score for schizophrenia than those who have bipolar disorder without symptoms of psychosis.

Although schizophrenia has some distinct genetic basis, research suggests that environmental factors also play a role in whether a person will likely develop the condition or not.

In other words, a person with a high genetic risk of schizophrenia may not necessarily develop it if other environmental factors are not there to “trigger” it.

Traumatic experiences early in life

A number of studies have suggested a correlation between traumatic experiences in childhood and adolescence and the development of schizophrenia in people with a genetic risk.

For people with a genetic predisposition to schizophrenia, the risk of onset for this condition is statistically higher for people who have experienced the following early in life:

According to a 2012 research review, some complications during pregnancy may play a role in triggering the genetic risk of developing schizophrenia.

Let’s take a look at what this review found.

Lack of oxygen during birth

The review found that fetal hypoxia, or lack of oxygen during birth, is associated with the highest genetic risk of schizophrenia.

Some obstetric complications causing hypoxia are:

The link between hypoxia and the onset of hereditary schizophrenia later in life could be more significant than smoking during pregnancy, microbial agents, and fetal development issues.

Bacterial and viral infections

Some bacterial and viral infections contracted during pregnancy across all trimesters, but especially in the second, could increase genetic risks of the child developing schizophrenia later in life.

According to the review, children had an elevated genetic risk of developing schizophrenia if their mother contracted any of the following during the second trimester of pregnancy:

This may be due to an activated immune response in the baby, triggering an inflammatory response. The review suggests this could affect brain development at puberty, increasing risks of developing schizophrenia.

Prenatal diet and sunlight

Children whose mothers had limited access to a nutritious diet during pregnancy could also have a higher genetic risk of schizophrenia.

The review suggests that eating a prenatal diet rich in the following nutrients could be vital in lowering a genetically at-risk baby’s chances of developing schizophrenia later in life:

  • folate (B vitamins)
  • proteins
  • essential fatty acids
  • vitamin A
  • vitamin D

One thing to keep in mind is that insufficient vitamin D during pregnancy isn’t always associated with access to nutritious foods. Instead, it can be related to less sunlight and time outdoors.

Because of this, the review noted that children born in the winter and spring carry a slightly higher genetic risk of schizophrenia.

Having an older father

For children who have schizophrenia or psychosis in their family, the genetic risks of developing the condition may increase by threefold if their father is 55 or older, according to the research review.

This is partly due to gene mutations in sperm, which increase with every decade the father ages. However, this could also be due to elevated exposure to environmental toxins over time, like air pollution.

Minimizing contact with toxins may reduce the risk of children developing schizophrenia.

Family environment seems to play a role in triggering schizophrenia development. A stressful or “unhealthy” family environment can worsen the risk, while a more calm one can act as a strong protective factor in people with a genetic predisposition for the condition.

According to a Finnish adoption study, researchers saw how genes and environment might interact to determine a person’s risk of schizophrenia.

In the study, adopted children whose biological mothers had schizophrenia-spectrum disorder were compared with adopted children of mothers without the diagnosis.

The adoptive families were later evaluated by psychiatrists as either “healthy” family environments or “unhealthy” family environments. Researchers defined an unhealthy family environment as one that was stressful, highly critical, conflict-ridden, and had problems with boundaries.

According to the study’s findings, of the adoptees with a high genetic risk of schizophrenia placed in an unhealthy family environment, 36% of them developed a psychotic disorder.

In contrast, only 6% of those with a high genetic risk placed in an environment deemed “healthy” by the study developed psychosis.

For the adoptees with low genetic risk, the family environment they were placed into did not contribute either way to onset of psychosis.

Schizophrenia is an inheritable disorder tied to the genetics of your first-degree relatives. But even if you carry a high genetic risk, it doesn’t necessarily mean you will develop schizophrenia in your lifetime.

This mental health condition often needs many more factors to trigger its development in most people with a genetic risk.

There are many effective methods to manage schizophrenia, including various forms of therapy, medication, and self-care.

You may need to try multiple things or a combination of measures to find what works best for you, such as:

  • Atypical antipsychotics. This first-line schizophrenia treatment comes in tablets, solutions, and longer-term injections. The drugs lower dopamine and sometimes block a serotonin receptor (5HT2a) to treat symptoms of psychosis and balance dopamine overall.
  • Psychosocial therapies. Social skills training, cognitive behavioral therapy (CBT), cognitive remediation, and social cognition can all help people with schizophrenia manage difficulties with social functioning caused by this condition.
  • Diet. Some studies suggest that following a keto diet — a low carb, high fat diet — may reduce symptoms of schizophrenia.
  • Social support. Joining support groups for people living with schizophrenia in person or online could be beneficial for your well-being.
  • Enjoying hobbies. Spending time engaging in activities you find enjoyable and relaxing can ease stress and manage symptoms of psychosis.
  • Sleep and exercise outdoors. Try to get enough sleep and exercise outdoors to support your overall wellness.

If you’re experiencing symptoms of schizophrenia, you are not alone. For more information on how to feel better now, visit the American Psychiatric Association.