Children with autism who come from minority backgrounds are more delayed than their Caucasian peers with the disorder, researchers say, likely because their symptoms go unnoticed longer.

The differences between white children and their non-white peers are significant, spanning everything from language to communication and gross motor skills, according to a new study published in the Journal of Autism and Developmental Disorders.

Researchers at the Kennedy Krieger Institute in Baltimore assessed 84 toddlers with autism from a variety of ethnic backgrounds.

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“We found the toddlers in the minority group were significantly further behind than the non-minority group in development of language and motor skills and showed more severe autism symptoms in their communication abilities,” said Rebecca Landa, director of the institute’s Center for Autism and Related Disorders who worked on the study.

The differences between ethnic groups persisted even when the researchers controlled for socioeconomic differences, they said.

Statistically speaking, autism is estimated to occur in 1 in 110 American children, but is not believed to be more or less common among members of any particular racial or ethnic group. However, previous research has indicated that white children tend to be diagnosed earlier than those who are African American, Hispanic or Asian, the researchers behind the current study said.

“It’s really troubling when we look at these data alongside diagnosis statistics because they suggest that children in need of early detection and intervention are not getting it,” Landa said.

While it’s unclear exactly why children from minority backgrounds are diagnosed with autism later, the researchers said it could be related to cultural differences in how people perceive childhood development. The ethnic disparity could also be due to stigma about disability in some communities.

What’s more, the researchers said they could not rule out the possibility that there may be biological differences in the manifestation of autism among different ethnic groups contributing to the more pronounced delays observed in children from minority backgrounds.