Counter to some previous research, a new study finds “no association” between a family’s income level and their child’s odds of having autism or intellectual disability.

The research, published this month in the journal Autism Research, is based on a study of more than 26,000 Utah children born in 1994.

Using government data on disability prevalence, birth certificates and tax information, researchers at the University of Utah assessed a variety of factors including gender, parental age, ethnicity and household income, comparing children with and without autism and intellectual disability.

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While gender and parental age did appear to affect a child’s odds of having one of the developmental disabilities, income did not.

The development came as a surprise, the researchers said, since some previous studies in the United States have found autism to be more common among children from higher income families and intellectual disability more likely among those with lower earnings.

“Demographic risk factors, such as male gender and parental age have been well-described,” said Judith Pinborough-Zimmerman, a researcher at the University of Utah who led the study. “However, the way in which socioeconomic factors are associated with the development of (autism) is poorly understood.”

Some variation with other studies could be due to regional differences in income and access to services, Pinborough-Zimmerman and her colleagues indicated.