Understanding Autism

Some people have a mild form, others a type that makes it hard to talk or interact with others

One in every 68 children born in the United States develop some form of autism. The disorder can, in some instances, lead to extreme social isolation or intense overreactions to sounds and other sensory stimuli.  


Editor’s note: Since this explainer was first published, a lot has changed in our understanding of autism as well as its terminology. Please refer to our updated explainer.

Autism refers to a group of closely related disorders that affect how the brain develops. Experts use one blanket term —“autism spectrum disorders” —to refer to the whole group.

Autism isn’t a disease that can be passed from one person to another. Nor do the vaccines commonly given in childhood cause autism, scientists say. The disorder appears to be due, at least in part, to the genes we inherit from our parents. However, scientists say genes alone can’t explain why some kids get autism and others don’t. Many other still-unknown causes likely contribute.

Autism emerges when certain parts of a child’s brain don’t develop as they would typically. The disorder often causes affected people to have trouble interacting with others. People with autism may struggle to communicate. They also may repeat some particular behavior or action over and over.

Although no one knows why, autism is becoming more common. About one out of every 68 U.S. children are being diagnosed with an autism spectrum disorder. Boys seem to be at much greater risk. In fact, doctors diagnose 1 out of every 42 boys with autism but only 1 out of every 189 girls.

Changes in certain genes have been linked to autism. Boys appear to need far fewer of these changes (or mutations) to develop the disorder. That was the conclusion of a study published March 6, 2014, in the American Journal of Human Genetics

Researchers use the word “spectrum” because the symptoms of autism can vary greatly from one individual to another. Some children may develop a mild version that’s barely noticeable. It’s called Asperger’s syndrome, or sometimes high-functioning autism. People with it may have no trouble speaking, thinking or remembering things. In fact, they often have excellent language skills. They can, however, find it hard to interact with other people. Some are clumsy, repeat the same actions or use odd words when they talk.

Others can have a more severe form of autism. In some cases, they will not be able to talk or take care of themselves.

Some scientists like to say that the brain is “wired differently” in people with autism. That means they often see, hear and feel the world in ways that others do not.

Bryn Nelson is a former microbiologist who now writes about science and lives in Seattle, Wash. He loves stories about medicine, microbes and the natural world. He drinks way too much coffee and has a playful dog named Piper.

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