Not everybody with autism spectrum disorder has the same difficulties. Some people may have autism that is mild. Others may have autism that is more severe. Two people with autism spectrum disorder may not act alike or have the same skills. Some people with autism are especially good at music or computers or art — just like other teens. Others may have trouble with speech and balance and coordination (just like other people!).
About 40% of people with autism spectrum disorder have average or above-average intelligence. The other 60% have intellectual disabilities that range from mild to severe.
Autism is four times more likely to affect boys than girls, and is found in all racial, ethnic, and social groups. There is no known single cause for autism, although the best available science points to important genetic components.

What Causes Autism?

Right now, doctors and researchers don't fully understand what causes autism. Scientists believe it has something to do with genes and environmental factors. New research has found that people are more likely to have a spectrum disorder if someone else in their family has one, but this doesn't necessarily mean that autism is passed down from parents to children. And autism definitely isn't contagious — you can't catch it from someone else.
Some studies suggest that something in the environment could make kids more likely to develop a spectrum disorder, but so far scientists haven't identified what that thing might be. Other studies have suggested that autism could be caused by viruses, allergies, or vaccines. But none of these theories have been scientifically proven. Most of the scientific studies on vaccines have found no link between vaccines and autism.
Dr. Leo Kanner first described autism in 1943. He reported on eleven children who showed a marked lack of interest in other people, but a highly unusual interest in the inanimate environment. Initially, autism was thought to be an early form of schizophrenia, which led to the belief that its onset could be caused by negative experience or bad parenting. We now know that this is not the case.