U.S. autism rates rise 15 percent; New Jersey rates remain highest

The report, released April 26, found that one in 59 children had autism, up an average of 15 percent from two years ago, in the 11 states included in the study. New Jersey's rate was the highest of the states studied - one in 34, up 19 percent from two years ago. That puts the national rate of autism at 1.7 percent of the childhood population and New Jersey's autism rate at 2.9 percent.

New Jersey is known for excellent clinical and educational services, so higher rates of autism in New Jersey are likely due to more accurate or complete case finding.

Walter Zahorodny, an associate professor of pediatrics at Rutgers New Jersey Medical School who directed the New Jersey portion of the study, called the results "consistent, broad and startling." He said the analysis shows U.S. autism rates are continuing to rise rather than leveling off as the 2016 CDC report suggested. "It is now clear that what we saw in 2016 was just a pause along the way. It remains to be seen at what point ASD rates will plateau," he said.

Zahorodny joined researchers in Arizona, Arkansas, Colorado, Georgia, Maryland, Minnesota, Missouri, North Carolina, Tennessee and Wisconsin in analyzing information collected from the health and special education records of 325,483 children who were 8 years old in 2014. They used the guidelines for ASD in the fourth edition of the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders for their primary findings, but also reported ASD estimates according to the definition provided in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders.

Across the network, the researchers found the prevalence of ASD ranged from a low of 13.1 per 1,000 children in Arkansas to a high of 29.3 per 1,000 children in New Jersey. ASD is four times more common among boys than among girls and white children are more often diagnosed with ASD than black or Hispanic children.

Although the estimates are not representative of the country as a whole, they are considered the benchmarks of ASD prevalence, Zahorodny said.

The researchers can't explain why autism rates have been increasing across the United States. Factors associated with a higher risk of autism include advanced parental age - children of parents over 30 have heightened risk, which increases with parental age - maternal illness during pregnancy, genetic mutations, birth before 37 weeks gestation and multiple birth.

"These are true influences that are exerting an effect, but they are not enough to explain the high rate of autism prevalence," said Zahorodny. "There are still undefined environmental risks which contribute to this significant increase, factors that could affect a child in its development in utero or related to birth complications or to the newborn period. We need more research into non-genetic triggers for autism."

Children who are diagnosed early often respond better to treatment, said Zahorodny, who notes the average age of diagnosis - 53 months - has not changed in 15 years.

"Despite our greater awareness, we are not effective yet in early detection," he said. "Our goal should be systematic, universal screening that pediatricians and other health providers provide at regular visits starting at 18 months to identify ASD as soon as possible."