Mental health conditions often have a hereditary link and one question always comes first, is schizophrenia genetic?
The latest research provides compelling evidence that genetics play a major role. New studies have identified over 100 genes associated with schizophrenia risk. While environment influences the development of schizophrenia too, genetics account for an estimated 65-80% of the risk. The hunt continues for specific genetic variations that contribute to schizophrenia.
According to WHO;
Schizophrenia affects approximately 24 million people or 1 in 300 people (0.32%) worldwide. This rate is 1 in 222 people (0.45%) among adults (2). It is not as common as many other mental disorders. Onset is most often during late adolescence and the twenties, and onset tends to happen earlier among men than among women.
The Genetic Link: Studies on Schizophrenia Risk and Family History
Research clearly shows that genetics play a major role in schizophrenia risk.
Family Studies
Family studies have found that having a close relative with schizophrenia increases your risk of developing the disorder. Siblings of those with schizophrenia have a 10% chance of developing it, while the general population only has a 1% risk. Twin studies also show that identical twins, who share very similar genes, have a 40-50% chance of both developing schizophrenia if one twin has the disorder. This is compared to only a 5% chance for fraternal twins.
Genome-Wide Association Studies
The comprehensive study published by Schizophrenia Working Group of the Psychiatric Genomics Consortium in 2014 analyzed the genomes of over 36,000 people with schizophrenia and 113,000 healthy controls. It found 108 genetic locations that were associated with the risk of schizophrenia. These locations spanned across many chromosomes and included both common and rare gene variants. The study provided the strongest evidence yet that schizophrenia has a substantial genetic component.
GWAS have identified several gene variants associated with increased schizophrenia risk, known as single-nucleotide polymorphisms or SNPs. The ZNF804A gene, for example, has been linked to psychosis and schizophrenia in multiple studies. Several other gene loci, including TCF4, NRGN, and MHC region genes, also show associations. Though individually these gene variants only slightly increase risk, together they point to biological pathways that may be involved in schizophrenia development.
Rare Genetic Variants
Rare genetic variants, including copy number variants (CNVs), have also been implicated in schizophrenia. Deletions or duplications of certain regions on chromosomes 1, 15, and 22, for example, have been associated with higher schizophrenia risk. These CNVs are thought to disrupt gene expression during neurodevelopment, which may contribute to the disorder.
While genetics clearly plays a role, environment and experience also shape a person’s risk of developing schizophrenia. The interplay between genes and environment, known as the “stress-diathesis” model, is currently thought to best represent the development of this complex disorder. By gaining a better understanding of the genetic factors involved in schizophrenia, researchers hope to develop improved treatments and even ways to prevent the disorder from developing in those at high genetic risk.
The Latest Study Providing Evidence of Genetic Factors in Schizophrenia
The largest ever study of its kind.
Over the past five years, geneticists led by the Broad Institute’s Stanley Center for Psychiatric Research and its collaborators around the world collected more than 100,000 human DNA samples from 30 different countries to locate regions of the human genome harboring genetic variants that increase the risk of schizophrenia. Analyzing data from over 77,000 people with schizophrenia and 243,000 control subjects without the disorder, the study identified 108 genetic locations that appear to influence a person’s risk of developing schizophrenia.
Strong evidence for a genetic component.
The study provides some of the strongest evidence yet for a genetic component in schizophrenia. While environment and life experiences also play a role, the findings suggest that genetics may account for up to one-third of a person’s susceptibility. The discovery of these 108 genetic locations helps point researchers to biological pathways that may be involved in the development of schizophrenia.
An important step forward but more work is needed.
While an important step forward, more research is still needed to translate these genetic findings into a better understanding of schizophrenia and improved treatments. The identified locations only account for a portion of the genetic risk, suggesting that many more genetic contributors have yet to be discovered. By continuing to study larger groups of people, researchers aim to identify additional genetic variations and gain new insights into how genetics and environment interact to cause schizophrenia.
Other Recent Studies on the Genetics of Schizophrenia
A number of other studies in recent years have provided further evidence for a genetic basis of schizophrenia.
Rare gene variants with big impact
Some studies have focused on rare gene variants that may have a large impact on schizophrenia risk. For example, a study of people with childhood-onset schizophrenia found that rare mutations in a gene called SETD1A were enriched in these individuals. SETD1A is involved in regulating gene activity in the brain during development. Rare mutations in other genes involved in brain development and connections, like NRG1 and NRXN1, have also been linked to schizophrenia.
Complex interplay between genes and environment
While genetics clearly plays a role in schizophrenia, environment and experience also significantly impact the development of the disorder. Genetics may influence a person’s vulnerability or resilience to environmental and psychological factors that can trigger the onset of schizophrenia. The interplay between genetic risks and environmental stressors is complex, and researchers continue to study how these factors interact in schizophrenia.
The accumulating evidence from many studies using diverse methodologies points to a strong genetic component in schizophrenia. However, schizophrenia is not determined by genetics alone. Environmental and psychological influences also play a significant role in the development and onset of the disorder. Understanding the complex inter relationships between these factors will be key to gaining a complete picture of the causes of schizophrenia.
A stressful family environment can exacerbate the risk of schizophrenia in genetically predisposed individuals, while a supportive environment may act as a protective factor
What Do These Studies Mean for Our Understanding of Schizophrenia?
As more genetic studies point to schizophrenia having a strong hereditary component, what do these findings mean for you or your loved one living with the condition? For starters, it shows that schizophrenia is a real medical disorder, not the result of bad parenting or a weak character. The genetic links prove it’s a disease of the brain that runs in families.
Improved Diagnosis and Treatment
With a better understanding of the genetics involved, doctors can work to improve diagnosis and develop targeted treatments. Detecting risk genes may help identify schizophrenia earlier, allowing for preventative treatment. Personalized medicine tailored to a patient’s unique genetic profile could also lead to better outcomes and fewer side effects.
Reduced Stigma
Knowing schizophrenia is biologically based can help reduce the stigma around mental illness. Too often, people with schizophrenia face discrimination and isolation due to misperceptions about the cause and nature of the disease. Genetic studies are helping to educate the public that schizophrenia is not due to a character flaw or poor upbringing.
Risk Assessment
Identifying the genes involved allows for genetic testing to determine a person’s risk of developing schizophrenia. Those at high risk could benefit from close monitoring, early intervention, and treatments to possibly delay or prevent the onset of symptoms. However, genetic testing also raises ethical issues regarding privacy and discrimination that must be considered.
New Drug Targets
Learning more about the biological mechanisms behind schizophrenia could reveal new targets for drug development. Researchers are studying how the genes implicated in schizophrenia interact with each other and impact the brain. This may lead to new treatments aimed at specific genetic and neural pathways involved in the disorder.
While genetics clearly play a role in schizophrenia, environment and experience are also important factors. Genes alone do not cause the disease, they just make certain individuals more vulnerable.
Genetic linkage and gene expression studies have identified the alpha 7 nicotinic receptor gene as abnormally expressed in individuals with schizophrenia, which could be a target for new drug treatments.
Conclusion
The latest research provides pretty compelling evidence that schizophrenia does indeed have strong genetic roots. While environmental factors can influence the development and severity of the disorder, your genetic makeup seems to be the primary predictor. The more relatives you have with schizophrenia, the higher your risk. New studies tracking specific gene variants associated with schizophrenia risk further confirm the hereditary link.
But remember, genetics aren’t destiny.
Even if you have the genes, you may never develop schizophrenia.
