More children are being diagnosed with and treated for autism spectrum disorder due to state mandates requiring commercial health insurers to provide services to these children, according to new research from the University of Pennsylvania. Still, they found, far too few children who need help are getting it.

The study results were published Monday in JAMA Pediatrics.

Researchers found that from January 2008 to December 2012, states that required private insurers to cover care had higher rates of diagnoses: 1.8 per 1,000 children, on average, as opposed to 1.6 per 1,000 in states without a mandate.

Since 2001, 44 states have adopted such mandates, including New Jersey and Pennsylvania.

The Penn researchers found that the effect of the mandates increased over time.

Still, the estimated rates fall well below the approximately 15 per 1,000 U.S. children, which the federal Centers for Disease Control and Prevention (CDC) estimates are on the autism spectrum, according to research team leader David Mandell, director of Penn's Center for Mental Health Policy and Services Research.

The study's findings "are clearly an improvement, but they are not sufficient," Mandell said.

During the study period, 154,089 children out of nearly 1.05 million in the researchers' sample were diagnosed with autism spectrum disorder.

The study examined insurance claims for children 21 and younger covered by United Healthcare, Humana, and Aetna.

Michael Rosanoff, director of public health research for Autism Speaks, a major advocacy and research organization, said the private insurance mandates are improving access to coverage. However, he said, "there still exists a large gap in access to services not being addressed by commercial insurance mandates alone."

The study looked only at private insurers. But Medicaid, the public insurance program for the poor, also has increased autism services, though "the implementation of that benefit has been unevenly applied," said Deborah M. Spitalnik, a pediatrics professor at Robert Wood Johnson Medical School.

Autism is a developmental disability characterized by impairments in social communication and repetitive behaviors.

New Jersey, with 1 in 41 children believed to be on the spectrum, ranks highest in the nation, according to the most recent CDC estimates, which cover just 11 states. The reasons for New Jersey's rate are controversial, though some experts believe it's in large part because the state has stricter rules requiring medical professionals and others to report autism diagnoses. Pennsylvania is not one of the states in the CDC's study.

Other estimates, including another federal figure, say the occurrence of the disorder across the nation is even higher.

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