Is autism genetic?

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that is thought to result from a combination of genetic and environmental factors. ^[1]

Impact of genes on ASD

While the cause of ASD may be known in some individuals and not known in others, research shows that genetic factors plays a key role. Folstein and Rutter’s landmark 1977 study on 21 pairs of British twins found that identical twins were more likely to have autism than non-identical twins. ^[2] This was the first study to establish a link between genetics and autism. 

With the aid of technological advances since, such as high-throughput sequencing in the early 2000s, exhaustive genetic research has discovered hundreds of genes related to autism, with hereditary rates estimated to be between 40 and 80 percent. ^[2]

Family history of ASD

Having a family history of ASD makes it more likely your children will have ASD. If you have a child with ASD, there is a greater likelihood your next child will have ASD. There is also a greater chance a relative of yours will have a child with ASD. ^[3]

If you are planning on having a baby, inform your doctor of yours, and your partner’s, family history of ASD. Your doctor can use this information to assess how likely you are to have a child with ASD.

Additionally, knowing about your family history of ASD can better equip your doctor to care for your child. ^[3] They can examine your child in the early stages of their development for early signs of ASD and refer you to a specialist as soon as they suspect its presence.

The younger your child receives an autism diagnosis, the more effective their treatment. Early intervention is key to providing better outcomes for children with autism ^[3]

Genetic testing and ASD

If your child is diagnosed with ASD, a doctor may refer your child for genetic counselling or testing. ^[3]

Through scrutinizing family medical histories, genetic counselling provides you with information about inherited conditions that affect you and your child. You will learn the risks and benefits of genetic testing and the different options that are available to you.

The aim of genetic testing will be to identify causes of ASD in an individual. The most prescribed test for people with autism is called a chromosomal microarray (CMA). ^[3] CMA reveals a genetic cause in 5-14% of people with ASD who take the test. ^[3]

Following genetic testing, your family will undergo further genetic counselling to help you understand the test results and what implications they have for your child going forward.

Irrespective of whether you have a family history of ASD, consult a doctor if you are worried about your child’s development.

Genetic link between ASD and other conditions

Research strongly indicates that people with certain genetic disorders, such as tuberous sclerosis, Down syndrome, fragile X syndrome or Rett syndrome, are more likely to have ASD. ^[3]

Numerous genetic studies have also shown links between genes related to ASD and other mental disorders and psychiatric conditions, such as schizophrenia and bipolar disorder. ^[2] These indicate some degree of mutual etiology across psychiatric conditions, despite clear differences in the way people present symptoms of autism^[2].

Sex ratio of people with ASD

Autism affects males four times as much as women. ^[1] The cause for this has not been definitively established, although it may due to a stigma surrounding what autism looks like and therefore missing detection of the disorder in females.