Autism Q & A: Is autism genetic?

By Daniel B. Kessler, M.D.

If you have one child with autism will your second child have autism, too? What about other relatives?

We do believe that there is a strong genetic component to autism. We know this in part from twin studies. If you have two identical twins and one is autistic, the chance the other twin will be autistic is between 60 and 90 percent (with 60 percent having the same diagnosis and 90 percent having related but less severe disorders). It’s not 100 percent, so more than just genes are involved here.

The risk that an infant with an older sibling with autism also will develop autism had been estimated to be between 3 and 10 percent but these figures came from older studies and involved smaller numbers of twins. Recently, the largest study of younger siblings of children with autism identified an average of almost 19 percent who had an autistic spectrum disorder.

Males were more likely to receive that diagnosis by almost threefold (26.2 percent in males and 9.1 percent in females) and if a child had more than one older sibling with autism then the risk to 32.2 percent. This study highlights the importance of routine surveillance and rapid referral for treatment of infant siblings of children with autism.

Related areas of difficulty and unusual characteristics that are seen in relatives (lesser-affected twins, siblings, parents, uncles and cousins) of the child with autism are referred to as the “broader autistic phenotype” and may include delayed language, obsessive tendencies, social challenges or quirky behaviors. (“Phenotype” is the expression of an inherited trait, such as anxiety or obsessive tendency, or physical characteristic such as low muscle tone.)

What if you have a family member with autism? Are you at risk of having a child with autism? There is no simple answer. It will depend on the cause of autism in the individual affected and that differs from child to child. It will be more predictable in the individual with an identifiable genetic disorder. If an individual has autism from an identified environmental toxin, such as lead, the risk to another family member would be very small.

An interesting side note about twin studies in autism.  They provided the proof of “biological origin “needed to combat the prevailing psychoanalytic theory of Bruno Bettelheim that attributed autism to bad parenting — particularly cold, unavailable, “refrigerator” mothers.  Much credit also goes to Bernard Rimland, Ph.D., a psychologist and autism expert who founded the Autism Society of America as well as the Autism Research Institute.

Rimland’s book, Infantile Autism: The Syndrome and Its Implications for a Neural Theory of Behavior, was instrumental in refuting the psychoanalytic theories of the 1960s, though Rimland later became more controversial in his championing of alternative causes and treatments for autism outside the scientific mainstream. Rimland died in 2006 at the age of 78.  His son Mark, diagnosed with high functioning autism and a talented artist, was the driving force behind his father’s and mother’s lifelong mission.

Next: The environmental causes of autism.

Daniel B. Kessler, M.D., is a developmental and behavioral pediatrician and medical director of the Children’s Developmental Center at Easter Seals Southwest Human Development. His private practice, where he provides evaluation and treatment for children and adolescents, is located at Southwest Human Development.

The views he expresses in this series are based on his training, his reading of the literature and his more than 30 years of experience taking care of hundreds of kids on the autism spectrum. The series begins here.


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