Exploring the causes of autism spectrum disorders

Research is showing autism may be rooted in genetics

Autism Spectrum Disorder is a developmental disorder characterized by difficulty with social relationships and communication. Repetitive and stereotypical behaviors may also be present. The symptoms often develop slowly, but there are some cases when the symptoms start suddenly. Most children are diagnosed between two and three years old, when difficulties with communication are noticed. Autism spectrum disorders can be associated with intellectual disabilities, developmental delays and physical health issues.

Research has shown that there is no one cause for autism. Many cases of autism are thought to be caused by both a genetic predisposition and environmental factors. Studies performed on twins and families with autism have proven that autism has a genetic basis.

With identical twins, who share all the same genes, when one twin has autism there is a 90 percent chance that the other twin will also have autism. There are many different genes involved in autism, so it can be difficult to find the exact gene involved in each individual or family. Currently, a genetic cause can be identified in about 15 percent to 20 percent of individuals with an autism diagnosis. As testing improves, and more genes are found, it is expected that a genetic diagnosis or predisposition will be identified in more individuals with autism.

In some individuals autism is caused by a metabolic condition. A metabolic condition is when the body is unable to digest and breakdown food properly. Although this is a rare cause of autism, when a person is found to have a metabolic condition, treatments such as medicine or changes in diet are often recommended to treat the individual’s symptoms.

A more common cause for autism is a genetic condition or syndrome. Genetic conditions happen when there is a change in an individual’s DNA or genes. There are many different genetic conditions that can cause autism. When an individual has a specific genetic condition, information may be available that can help the family know more about what to expect. Knowing the diagnosis may predict what medical issues the individual will develop in the future, allowing the individual to be monitored more closely by their doctor. Having a specific diagnosis also helps families find support groups and make connections with other parents who have children with the same condition.

Genetic and metabolic conditions can happen for the first time in an individual, but they can also be inherited. In some individuals with autism, the abnormal gene was inherited from a parent who does not have any signs of autism. This means that even when no one else in the family has autism, it can still be genetic. Families often find it important to know if the child’s condition is genetic when they are thinking of having another child. When there is a genetic diagnosis, more information is available about the chances of future children or other family members to have the same condition.

Because autism can often be genetic, it is recommended that individuals with autism be evaluated by a medical geneticist and a genetic counselor to see if a genetic cause can be found for their autism diagnosis. Anyone interested in a genetics consultation can request a referral from their pediatrician or family doctor.

Jillian Ozmore, MS, LGC works in CHaD Medical Genetics at Dartmouth-Hitchcock Specialty Care at Bedford Medical Park, Dartmouth-Hitchcock Manchester, Dartmouth-Hitchcock Nashua and Dartmouth-Hitchcock Medical Center. For more information, go to chadkids.org/genetics.

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