Both genetics and environmental factors can cause autism. Autism genetic testing may offer information about why your child is autistic.

Genetic testing may be able to uncover whether your child has some of the genes associated with autism.

Test results can influence how your child’s care team will monitor and manage their condition. There may be tailored treatments available, or access to a clinical trial, depending on what genetic testing reveals.

Testing can also provide information about what to expect in your child’s specific circumstance, as well as offer insight into the chance of recurrence in a future younger sibling.

Genetic testing looks for potential autism causes that might be present.

Syndromic autism is an example of how genetic testing may be applicable. This is the type of autism that occurs with another condition, like Down syndrome or fragile X syndrome, which can be identified with targeted genetic testing.

Syndromic autism is also called secondary autism. Other common causes include tuberous sclerosis and congenital infection like cytomegalovirus. Researchers estimate that secondary, or syndromic autism, comprises about 15% of autism diagnoses.

Because some of the conditions that occur with syndromic autism cause visible differences in your child, they’re often diagnosed first. Down syndrome is an example and is usually diagnosed at or before birth through genetic testing.

Idiopathic autism, or autism from an unknown cause, is harder to find with a genetic test. This type of autism occurs on its own, without another condition. These cases make up around 85% of autism diagnoses.

Genetic analysis is usually done using a test called a chromosomal microarray (CMA). This test looks for CNVs, which are small gene changes in the form of extra and missing pieces.

CMA is typically recommended to be done if a specific genetic syndrome isn’t identified as the cause of a child’s autism. But it’s not recommended for genetic syndromes that cause secondary autism.

This type of test usually finds a genetic cause for autism between 5.4% to 14% of the time.

Technicians perform a CMA test from a blood sample. They compare the sample to another sample containing typical, unaltered DNA.

Sometimes there’s evidence to suggest there’s a genetic difference even when the CMA test doesn’t find one.

In this case, your child’s doctor might recommend whole exome sequencing, which assesses the protein-coding regions of your child’s genome.

Deciding the exact testing to be done can be complicated, and should be individualized for each child. Consider speaking with a pediatric geneticist for help.

Genetic tests don’t diagnose autism. Instead, they look for factors that may increase the chance of autism occurring.

Test results can also indicate if your child is prone to other issues, like seizures or kidney problems, for example.

Symptoms that accompany your child’s autism might be from a genetic difference and having this information can help doctors determine the best treatment for your child.

But genetic testing isn’t used to diagnose autism.

Can autism be detected during pregnancy?

It may be possible to determine if an unborn baby has a higher chance of being autistic. CMA testing can be done in both prenatal and postnatal settings.

When clinicians perform a CMA test during pregnancy, they obtain a sample of the amniotic fluid using an amniocentesis guided by an ultrasound. The amniotic fluid contains the baby’s genetic material, which they assess with the CMA test.

There have been hundreds of genes identified as potential contributors to autism, according to a 2019 review article published in Frontiers in Cellular Neuroscience.

The article explains that autism causes are both multigenic (mutations in multiple genes) and heterogeneous (more than one gene that produces the same or similar result).

Research is ongoing to clarify the numerous ways autism can be passed down from each parent.

A 2019 study found that autistic children and their mothers share altered expression of DNA containing human endogenous retroviruses (HERVs).

These are pieces of ancestral infections that have been integrated into human DNA. When HERVs are reactivated, they may contribute to cancer and disorders that are:

  • autoimmune
  • neurological
  • psychiatric

Researchers have found elevated levels of HERV-H in blood samples taken from autistic people.

The study also found that autistic children and their mothers share the expression of a recently identified gene called human endogenous MER34 ORF (HEMO).

Both HERV-H and HEMO were elevated in autistic children and their mothers, but low in typically developing controls.

A 2021 study found that epigenetic alterations have been found in the sperm of fathers with autistic children.

Epigenetics, or DNA methylation, refers to changes in the function of genes because of added methyl groups. This doesn’t change the gene sequence, only its expression.

Environmental factors are a significant cause of DNA methylation. These factors can include:

  • hormones
  • diet
  • drugs
  • stress
  • exposure to chemicals

When children inherit their parents’ DNA, they also acquire any epigenetic changes that have occurred.

Autism has more than one cause. Genetic testing may be able to determine if your child’s autism is genetic.

Doctors use a blood sample to analyze DNA. They look for missing or extra pieces, or changes to the sections that code proteins.

Test results can be helpful in several ways, like influencing condition monitoring and treatment decisions, as well as indicating the chances of a similar occurrence in a sibling.

If you think genetic testing would offer useful information, it may be worth having a conversation with your child’s doctor to learn more.