The study was small - just 48 children evaluated at the University of Washington - but the results were so encouraging it has been expanded to several other sites, said Geraldine Dawson, chief science officer of the advocacy group Autism Speaks. Dawson, a former University of Washington professor, led the research team.
Early autism treatment has been getting more attention, but it remains controversial because there's scant rigorous evidence showing it really works. The study is thus "a landmark of great import," said Tony Charman, an autism education specialist at the Institute of Education in London.
There's also a growing emphasis on diagnosing autism at the earliest possible age, and the study shows that can pay off with early, effective treatment, said Laura Schreibman, an autism researcher at the University of California at San Diego.
The National Institute of Mental Health funded the study, which was published online Monday in Pediatrics.
Children aged 18 months to 30 months were randomly assigned to receive behavior treatment called the Early Start Denver model from therapists and parents, or they were referred to others for less comprehensive care.
The therapy is similar to other types of autism behavior treatment. It focused on social interaction and communication - which are both difficult for many autistic children. For example, therapists or parents would repeatedly hold a toy near a child's face to encourage the child to have eye contact - a common problem in autism. Or they'd reward children when they used words to ask for toys.
Children in the specialized group had four hours of therapist-led treatment five days a week, plus at least five hours weekly from parents.
After two years, IQ increased an average of almost 18 points in the specialized group, versus seven points in the others. Language skills also improved more in the specialized group. Almost 30 percent in the specialized group were re-diagnosed with a less severe form of autism after two years, versus 5 percent of the others. No children were considered "cured."
Ashton Faller of Everett, Wash., got specialized treatment, starting at age 2.
"He had no verbal speech whatsoever, no eye contact, he was very withdrawn," recalled his mother, Lisa Faller.
Within two years, Ashton had made "amazing" gains, she said. Now almost 6, he's in a normal kindergarten class, and though he still has mild delays in social skills, people have a hard time believing he is autistic, Faller said.
The treatment is expensive; participants didn't pay, but it can cost $50,000 a year, Dawson said. Some states require insurers to cover such costs, and Autism Speaks is working to expand those laws.