Think of genes like recipes for the body. The data tucked inside each cell dictates how you look, grow, and feel. That information can be influenced, and sometimes even changed, by things that happen outside of your body.
Given the complexity of genetics, it's difficult to answer simple questions like, "Is autism genetic?" So many factors play a role.
Within the last several years, plenty of important studies wrapped up. Many of them suggest that autism is genetic — at least somewhat. Others highlight just how much remains unknown about the role genes play in autism.
We'll walk through what researchers say when asked if autism is genetic. And we'll highlight what else we should know before we can answer questions definitively.
The Role of Genes in Autism
Genes move from parents to children. In each child, two sets of genes compete for dominance. Sometimes, kids have exactly the same issues their parents do. Sometimes, siblings share genetic traits too. Studies done with families tell us a lot about how genetics play a role in autism.
For years, we've known that autism is a hereditary trait that can pass from parents to kids. The first study on identical twins, published in 1977, highlighted that fact. Researchers seem sure that when one identical twin has autism, there's an 80% chance the sibling has the disorder too. If the twins are fraternal, the risk drops to about 40%.
Researchers know that kids with autism spectrum disorder also have other genetic-based conditions, such as:
- 22q deletion syndrome.
- Angelman syndrome.
- CHARGE syndrome.
- Cornelia de Lange syndrome.
- Down syndrome.
- Duchenne muscular dystrophy (DMD).
- Fragile X syndrome.
- Prader-Willi syndrome (PWS).
- Rett syndrome.
- Smith-Lemli-Opitz syndrome (SLOS).
- Smith-Magenis syndrome (SMS).
- Sotos syndrome.
- Tuberous sclerosis.
About 20% of children with ASD have a syndrome like this, researchers say. Most of the conditions are caused by missing or extra pieces of DNA or other types of abnormalities.
It’s possible that autism and these other genetic conditions are linked, and that they pass from parent to child in a predictable manner researchers can detect.
Plenty of Genes Involved
Some genetic conditions are simple, and they stem from one unusual item found in one strand of DNA. Autism is much different, and that complexity makes the condition a lot harder to spot.
In January 2020, researchers published the results of a massive study that included:
- A large study group. More than 35,000 people sent in samples for analysis.
- ASD data. Of the 35,000 participants, almost 12,000 had autism spectrum disorder.
- Gene sequencing. Testing methods picked up rare mutations that might stay masked with other methods.
Per the results, more than 102 genes were attached to autism risk. This is a huge number, and researchers suspect that the genes intertwine and intermingle.
Some of them are associated with other developmental delays. Others seem to increase the risk of neurodevelopmental disorders.
The researchers don't yet know how the genes work, so parents can't walk into a laboratory and ask for an autism gene screening. There is too much data to look for and a lot we don't know.
But this study suggests that many genes, working together, could raise autism risks. That data could be helpful as researchers look for ways to treat, and perhaps even cure, ASD.
More Research Is Required
Knowing how many genes sit behind autism risk is important. Researchers stress that we just don't know enough about autism spectrum disorder to put our genetics knowledge to use quite yet.
Some researchers say that genes explain how cells work, and they can highlight how damage causes disease risk. Non-genetic risk factors for ASD are very real, including:
- Mitochondria. These tiny structures provide cell energy, and they have their own DNA. People with ASD often have unusual mitochondrial function, and that might cause a cascade of problems that leads to autism symptoms.
- Developmental susceptibility. Genes and environment intertwine in everyone. Someone with the right set of genes pushed toward the right prompt might develop ASD, while someone who avoids the trigger may never have a problem.
- Environment. Factors like twin pregnancies, inadequate folate intake during pregnancy, and more could enhance autism risks.
All of these risk factors could overrule the importance of genes in autism risk, or they could be a piece of the puzzle that makes the role of genetics clear. More scientific work is required to answer these questions.
Researchers also say some people develop autism without a family history of the disorder. In fact, they say, about 30% of cases happen like this. If the disease happens in people who have few or no genetic vulnerabilities at all, what does that mean in terms of a so-called "autism gene"? We don't have the answers to this question in 2020.
Every day, talented research professionals sit down with slides, samples, and data and attempt to puzzle out how our genetic data influences autism risk. But sometimes, the results bring up more questions than answers. As much as we want a clear picture, it's not available yet.
Why Do Genetic Studies Matter?
If it's hard to determine if autism is genetic, why do researchers keep working on the answer? Their work may seem futile, but the results matter for families, doctors, and children with autism.
For example, families have long worried about enhanced autism risk sparked by everyday activities. They worry about:
- A mother's dietary habits.
- A child’s dietary habits.
- Infections, including the flu.
Parents can grow so worried and distressed that they avoid lifesaving steps, including vaccinating children and exposing them to healthy foods. Genetic studies can bring relief.
For example, in a large study in 2019, researchers determined that 80% of autism risk came from genes, not the environment. This news was shared far and wide, and it laid some worries and fears to rest. Parents who blamed themselves for a child's ASD may have felt relief about the news too.
Gene studies may point the way to treatments and cures too. For example, a researcher duo in North Carolina is working on both detection and cure methods. One part of the pair examines genetic testing, so parents could spot the disorder in kids before symptoms appear. The other examines gene splicing, so damaged bits of data are removed before problems are noticed.
This is groundbreaking research, and it may be years before we hear if the theories translate into real-world solutions. The researchers have a lot of work to do before they can start in on therapies with families.
Without genetic research, they couldn't dream of a day when early identification and treatment was an option for families. They need to build on work done by others.
Other researchers use the data to consider personalized medicine. They say identifying gene sequencing issues could help doctors create very specific medication regimens to help their patients. The pills one person took would be very different than the pills another took.
Again, this work is very new, based on the latest science. Researchers need much more time to solidify plans and bring them to life, but the theories are interesting.
What Can Families Do Right Now?
Your family doctor can't offer you gene splicing. Some can't even provide genetic counseling. If you have autism and you are considering having kids, know that your children may have the same condition you do. If you don't have autism but someone in your family does, the risks may still be enhanced for your child.
If you have a child or loved one with autism, watch the results of studies. Talk over questions with your doctor. Look for ways to support charities that fund autism research. The more we know about this disease, the better.
- Autism Genetics, Explained. (June 2017). Spectrum.
- ASD and Other Genetic Conditions. (January 2020). The Children's Hospital of Philadelphia.
- What Causes Autism? Researchers ID 102 Genes Linked to Condition. (January 2020). Healthline.
- Beyond Genetics in Autism. Autism Research Institute.
- Autism Linked to Mutations in 'Junk' DNA and Not Specific Genes, Study Reveals. (May 2019). Neuro Central.
- Genetic Causes and Modifiers of Autism Spectrum Disorder. (August 2019). Frontiers in Cellular Neuroscience.
- Largest Autism Genetics Study Identifies 102 Genes Associated With the Condition. (January 2020). Mount Sinai School of Medicine.
- Identification of Common Genetic Risk Variants for Autism Spectrum Disorder. (February 2019). Nature Genetics.
- Genetics by Far the Biggest Factor in Autism Risk, Study Says. (July 2019). Huffington Post.