Is It Common for Siblings to Have Autism?

As a parent of an autistic child, you may want to know how likely it is that you will have another child with autism. This article will discuss whether research supports the likelihood of having multiple children with autism, if autism can be prevented, and when parents should be concerned.

Research on siblings and autism

Research has confirmed that a couple with an autistic child has a statistically higher chance of having another child with autism spectrum disorder (ASD). The probability of this happening largely depends on whether their first child’s ASD was produced by a known genetic condition or an unknown cause.

The various potential causes of ASD are still not fully understood, but researchers have discovered that up to 15% of autism cases can be linked to a genetic cause. For the parents of children with ASD related to a genetic cause, genetic testing can be performed to determine the likelihood of autism reoccurrence in subsequent children due to that specific genetic condition. Depending on the genetic condition responsible for causing the first child’s ASD, the likelihood of recurrence in subsequent children could be as high as 50%.

But what about children with ASD from an unknown cause? Many studies have been performed to assess the risk of having multiple children with autism. For a couple with one child with ASD from an unknown cause, the estimated likelihood of having another child with ASD is approximately 10%. If a couple already has two children with ASD, that probability may be as high as 35%.

Recent evidence has found no correlation between the sex of the child with ASD and the likelihood of a sibling also having the disorder.

Autism prevention – is it possible?

Autism spectrum disorder cannot be prevented, but there are things you can do to decrease the risk of your child having the disorder.

While the exact causes of ASD are still unknown, research has shown that certain risk factors increase the chance of a child having autism. These risk factors can include:

• Advanced parental age;
• Untreated hypothyroidism;
• Exposure to air pollutants and chemicals;
• Maternal substance use during pregnancy;
• Maternal obesity;
• Gestational diabetes;
• Certain maternal infections during pregnancy (ex. rubella, influenza);
• Certain genetic conditions.

It is important to understand that having one or more of these risk factors does not guarantee your child will have ASD, only that the risk is higher. Many scientific studies have been published to confirm that ASD is not caused by vaccines.

General prevention tips

Basic general prevention measures that parents can implement are:

• Weight. Maintaining a healthy weight.
• Diet. Eating a balanced diet.
• Habits. Avoiding alcohol and drug use.
• Environment. Avoiding harmful environmental factors (ex. smoke, carbon monoxide, air pollution, chemicals).
• Health. Visiting a healthcare provider regularly to assess for any underlying illnesses.

Finally, as previously mentioned, genetic testing is recommended for couples in order to assess for genetic conditions which have the potential to cause ASD.

When should you be concerned?

If you have a child with ASD, the chances of having another child with ASD are increased. It is recommended that you seek genetic counseling to try to uncover the cause of your child’s ASD. Doing so can give you a better understanding of how likely it is that you will have another child with ASD.

Younger siblings of children with ASD should be monitored closely for signs and symptoms. It is important to remember that ASD is a spectrum and symptoms can vary widely from child to child. If you already have a child with autism, your other children may not show the same signs and symptoms.

If you are concerned about the way your child is developing, or if you suspect your child may have autism, you should speak to your child’s healthcare provider immediately.