Genetic factors play a big role in causing autism spectrum disorder, but researchers suspect environment is also involved.
Autism spectrum disorder (ASD) is a neurodevelopmental condition — a group of conditions involving brain differences that can affect behavior, memory, communication, and learning.
Autism is complex, and no two autistic people are the same. Because of this, researchers believe there are probably many causes of autism, including genetic and environmental factors.
Many autistic people view autism as part of their identity — not as a condition to be treated or prevented. So, some people are now saying that research on its causes isn’t the best use of resources, since some of this is centered around prevention.
Some autistic people and advocates suggest research and resources that support autistic people are much more helpful.
Many experts believe genes play the biggest role in causing autism. A
While research suggests that many autistic people have small mutations in a lot of their genes, it’s not always clear how big of a role these mutations play.
In fact, many autistic people have different mutations, and some don’t show the genetic changes that are often connected to autism. This means that different mutations probably play different roles in causing autism.
For example, some mutations or combinations of mutations could:
- play a role in causing certain behaviors
- contribute to whether someone needs minimal or significant support
- increase a person’s chances of having autism
Other genetic factors that could increase someone’s chances of developing autism include:
- assigned male at birth
- having an autistic sibling
- a chromosomal condition like fragile X syndrome
Because we tend to have more control over environmental factors,
- the fetus is exposed to air pollution or certain pesticides before birth
- the pregnant parent has diabetes or another immune system disorder
- the baby is born before 36 weeks old
- there were birth complications like the baby was breech, in fetal distress, or had a low birth weight
- there were any issues during birth that caused a limited amount of oxygen to the baby’s brain
These factors likely don’t cause autism by themselves. For instance, many babies are born before 36 weeks, with and without autism.
Researchers have also looked into other biological factors connected to autism. These factors are involved with:
brain connectivity growth or overgrowthin certain areas of the brain metabolism(how the body produces energy)
The same research suggests that some infections during pregnancy could increase the child’s likelihood of having autism. Several other immune issues may also increase likelihood, including:
- problems with how the immune system works
- developing antibodies to a condition they haven’t been exposed to
Another possible factor linked to autism? How well an autistic person’s mitochondria (the “powerhouse” of the cell) work. Mitochondria create the majority of a cell’s energy and are an important part of metabolism, among other things.
Other factors that may play a role in someone’s chances of developing ASD include:
frontal cortexof the baby’s brain overgrows shortly after birth
- the baby is male (autism is
4 timesmore common in boys than girls)
An autism diagnosis may also be more likely if during pregnancy, the parent:
- had hypertension or diabetes
- experienced an antepartum hemorrhage in the third trimester or postpartum hemorrhage
- has given birth to more than 4 children
- had preeclampsia
Some people believe that vaccines cause autism. This isn’t true.
According to many organizations, including the
This belief comes from a study published in the British medical journal, Lancet, in 1998. The study concluded that the measles, mumps, and rubella (MMR) vaccine caused autism.
The study wasn’t properly conducted, and it was later retracted and disproven. But it gained a lot of publicity, and some people still believe the false findings are true.
Other factors, like smoking during pregnancy, exposure to mercury, or fertility treatments are also believed to cause autism. None of these causes have been proven.
Autism is diagnosed by a medical professional, often a pediatrician or specialist.
According to the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), an autistic person must have both social and behavioral patterns that meet the criteria for autism spectrum disorder.
Someone might receive an autism diagnosis at 18 months or younger, but it’s more common to get diagnosed around 2 years old.
Still, some people don’t get a diagnosis until much older or until adulthood.
When diagnosing ASD, clinicians may look for patterns in communication like:
- difficulty with back-and-forth conversation
- differences in nonverbal communication like facial expressions or body language
- difficulty adjusting behavior to different social settings
A doctor may also look at these behavioral patterns when screening for autism:
- specific movements, actions, or gestures
- strong attachment to routine
- specific, strong interests
- differences in sensory processing
Many autistic people see autism as an identity, not as a condition to be treated. But if you’re experiencing challenges related to being autistic, there are many ways to find support, depending on your needs.
When learning what kinds of resources your autistic child needs, it can help to research your options and talk to doctors. Deciding what’s best for your child will depend on the level of support they need and what’s available to you.
While there’s no single way to support autistic people, professionals often agree that the earlier you can connect with support services, the better. Many forms of support — especially for autistic children — can help them feel safe and understood.
Autism is complex. While genetics may be a key factor in causing autism, it’s likely that a person’s environment and other factors also play a role.
Researchers have found more than 800 genes linked to autism. While we still don’t know as much about environmental or biological factors, researchers have made progress.
No matter what causes autism, there’s plenty of opportunities for autistic people to live well and find the support that works for them.