New research shows that it often takes three years and visits to multiple providers before Black children are diagnosed with autism, denying them a critical opportunity for therapy when it’s likely to be most effective.

Autism can be reliably diagnosed before age 2, but most children aren’t flagged until after age 4. Black children, however, are nearly 5½ years old, on average, before they receive an autism diagnosis, according to findings published online Monday in the journal Pediatrics.

“This study reveals major roadblocks to receiving a diagnosis of autism, which has significant consequences for young children and their families,” said John N. Constantino, a professor of psychiatry and pediatrics at Washington University in St. Louis who led the research. “In our current national conversation about race, preventable disparities in diagnosis and treatment services deserve a high priority because failure to address these disparities may seriously compromise outcomes for children affected by autism. We must do better.”

The study looked at 584 Black children who visited autism specialty centers located in St. Louis, Atlanta, New York and Los Angeles. Researchers found that it takes Black children an especially long time to be noticed, with a diagnosis occurring an average of six months later than for their white peers.

This delay occurs even though parents of Black kids report conveying concerns about their children’s development for more than three years. Almost half of the parents of children in the study indicated that they saw multiple specialists before receiving a diagnosis.

There was no association between delayed diagnosis and access to health insurance, the researchers found. Likewise, the study offered no clear explanation for why Black children with autism are twice as likely as white kids to have intellectual disability too even though autism prevalence is largely consistent across racial groups.

“Remarkably, among the African American children with autism in the new study, intellectual disability was not related to the factors that usually predict cognitive strengths and weaknesses,” Constantino said. “Household income, the IQ levels of blood relatives and preterm birth often are linked to cognitive outcomes, but those factors did not explain the disproportionate burden of intellectual disability suffered by African American children with autism. There is an ethical imperative to determine whether leveling the playing field for the timing of diagnosis and the quality and quantity of developmental therapy might resolve this disparity.”