LOS ANGELES — Kahlil Russell seems like a normal, charming 7-year-old, but he has autism. He speaks only a few words and can quickly drift away to where no one — not even his parents — can reach him.
More from TODAY.com
Hillary Clinton: Granddaughter led me 'to speed up' political plans
Clinton said she is inspired to keep working to ensure that Charlotte and her generation are provided equal opportunities ...
- Lauren Hill, inspirational college basketball player, dies
- Marathon dad's victories help raise money for son with spina bifida
- Will it work on Vale? Savannah tries tissue sleeping trick at home
- Listen to the chilling 911 call Sandra Bullock made during break-in
- Hillary Clinton: Granddaughter led me 'to speed up' political plans
"We try to get Kahlil to try to kind of interact with us, but then I have to think and realize, you know, he's in his own world and he's doing his own thing," says Kahlil's father, Clifford.
Kahlil attends a school for children with the disorder run by the Help Group in Sherman Oaks, Calif. At the school, one can see the range of disabilities the brain disorder can cause — from mild to severe.
What goes on in the brains of these children?
"They see everything. They hear everything. They feel everything," says Dr. Michael Merzenich at the University of California at San Francisco. "But they can't tell anybody. They can't get it out."
Most troubling, experts say, is the alarming increase in the number of cases. A few decades ago, autism was almost unheard of. Now it seems to be exploding. In the past decade the number of school-age children getting treatment skyrocketed 600 percent.
"Parents are going to be needing more and more of these types of facilities with the increasing numbers of kids being identified," says Dr. Barbara Firestone, president of the Help Group.
Why the increase?
Dr. Daniel Geschwind at the University of California Los Angeles says one reason is that doctors are diagnosing it more often.
"People are less reluctant to diagnosis autism, or high-functioning autism, in children. And so, some of it is clearly a diagnostic issue," says Geschwind.
But that's not all. Research so far has cleared childhood vaccines, but there could be other environmental factors.
"This doesn't necessarily mean toxicants," says Geschwind. "It can be anything in the environment that we're exposed to."
To try to find the cause, researchers are scanning the brains of children and adults with autism and looking for genetic factors. They hope that a better understanding of this frightening disorder will help reveal the reasons behind the dramatic increase.
© 2013 NBCNews.com Reprints