ATLANTA - About one in 150 American children has autism, US health officials said Thursday, calling the troubling disorder an urgent public health concern that is more common than they had thought.

People walk along a sidewalk in a file photo. Autism is more common in the United States than anyone had estimated, affecting about one in every 150 children, the Centers for Disease Control and Prevention reported on Thursday. [Reuters]

The new numbers are based on the largest, most convincing study done so far in the United States, and trump previous estimates that placed the prevalence at 1 in 166.

The difference means roughly 50,000 more children and young adults may have autism and related disorders than was previously thought - a total nationwide of more than half a million people.

Advocates said the study provides a sad new understanding of autism's burden on society, and should fuel efforts to get the government to spend hundreds of millions of additional dollars for autism research and services.

"This data today show we're going to need more early intervention services and more therapists, and we're going to need federal and state legislators to stand up for these families," said Alison Singer, spokeswoman for Autism Speaks, the nation's largest organization advocating services for autistic children.

The study by the US Centers for Disease Control and Prevention was based on 2002 data from 14 states. It calculated an average autism rate 6.6 per 1,000, compared to an estimate last year of 5.5 in 1,000.

"Autism is more common than we believed," said Catherine Rice, a CDC behavioral scientist who was the study's lead author.

The research was based on 2002 data from all or part of 14 states. It involved an intense review of medical and school records for children and gives the clearest picture yet of how common autism is in some parts of the country, CDC officials said.

The results suggest 560,000 children and young adults have the condition.

However, the study population is not demographically representative of the nation as a whole, so officials cautioned against using the results as a national average. The study doesn't include some of the most populous states like California, Texas and Florida.

Also, the study does not answer whether autism has recently been on the rise - a controversial topic, driven in part by the contention of some parents and advocates that it is linked to a vaccine preservative. The best scientific studies have not borne out that claim.

"We can't make conclusions about trends yet," because the study's database is too new, Rice said.

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