Chicago ? In Washington state, Reza and Arzu Forough pay more than $1,000 a week for behavior therapy for their 12-year-old autistic son.

In Indiana, Sean and Michele Trivedi get the same type of therapy for their 11-year-old daughter. But they pay $3,000 a year and their health insurance covers the rest.

Two families. Two states. Big difference in out-of-pocket costs.

If autism advocates get their way, more states will follow Indiana’s lead by requiring health insurers to cover intensive and costly behavior therapy for autism.

In the past two years, six states – Texas, Pennsylvania, Arizona, Florida, South Carolina, Louisiana – passed laws requiring such coverage, costing in some cases up to $50,000 a year per child.

The powerful advocacy group Autism Speaks has endorsed bills in New Jersey, Virginia and Michigan and is targeting at least 10 more states in 2009, including New York, California and Ohio.

Other states, including Illinois, have similar bills in the works but aren’t working directly with Autism Speaks.

“This is the hottest trend in mandates we’ve seen in a long time,” said J.P. Wieske, a lobbyist for an insurance coalition that argues that these state requirements drive up insurance costs for everyone. “It is hard to fight them.”

Arzu Forough of Kirkland, Wash., who is pushing a bill in her state, credits behavior therapy for teaching her son Shayan, at age 3, to make a sound to ask for a drink of water. Now 12, he is learning to converse about his favorite food and music, and to talk about his frustrations rather than throw tantrums.

Shayan’s improvements are a welcome relief to his mother, who once called for police help with her out-of-control son while she was driving.

The Foroughs have health insurance, but it doesn’t cover Shayan’s therapy. Although they both work full time, they must live rent-free with her elderly mother to be able to afford his treatment.

Autism is a range of disorders that hinder the ability to communicate and interact. Most doctors believe there is no cure. An estimated 1 in 150 American children are diagnosed with it.

Supporters say behavior therapy has decades of research behind it and can save money in the long run by keeping people out of institutions. Researchers agree, but say much remains unknown about which therapy works best for autistic kids, whether long-term gains can be claimed, and whether it works with older children.

Some states require behavior therapy coverage up to age 18 or 21. But the scientific evidence for therapy is strongest for the youngest, ages 2 to 5. Some researchers have reported on individual children with autism who no longer appeared disabled when they reached school age.