Socioeconomics playing reduced role in autism diagnoses

"As knowledge has spread about autism, information is now more evenly distributed across different kinds of communities," said Peter S. Bearman, the Cole Professor of the Social Sciences at Columbia University and the Director of the Paul F. Lazarsfeld Center for the Social Sciences, who coauthored the study, which appears in the April issue of the American Sociological Review. "It is also easier to find someone who can diagnose autism, so we no longer see these huge differences in rates of diagnosis. However, it appears that poor kids living in poor neighborhoods still are not being diagnosed."

The study examines birth and diagnostic records for all children born in California between 1992 and 2000 in conjunction with individual and community-level data such as parental wealth, parental education, and neighborhood property value. All children were followed from the time of birth until June 2006 to allow ample time for diagnosis. As the disorder became increasingly well-known, the average age of autism diagnosis fell from 5.9 among those children born in 1992 to 3.8 for those born in 2000.

"At the height of rising prevalence, which involved children born between 1992 and 1995, kids whose parents had fewer economic resources simply weren't diagnosed as often as wealthier children -- wealthier kids were 20 to 40% more likely than poorer children to be diagnosed," said study coauthor Marissa D. King, an assistant professor of Organizational Behavior at Yale University's School of Management "Among children born in 2000, however, parental wealth alone had no effect on the likelihood that a child would be diagnosed."

Overall, of the 4,906,926 million children born in California between 1992 and 2000, 18,731 or .38% were diagnosed with autism. The prevalence of autism among the 1992 through 2000 California birth cohorts increased significantly, from 29 per 10,000 in 1992 to 49 per 10,000 in 2000.

"I think what has happened in California is that the ascertainment machinery -- a combination of diffusion of information, awareness, conversations, and the capacity of physicians, teachers, nursery school providers, nurses, and so on -- has become more established," Bearman said. "And, as more and more people are diagnosed with autism and the disorder becomes more central to thinking about child development in everyday discourse, the information about who might have autism is more evenly distributed across the whole state no matter where people live. So, the differences across communities and by social class are less than they used to be."

But, Bearman said, it is still the case that children from low-income families who live in poor neighborhoods are less likely to be diagnosed with autism. "We know that parents talking to each other about navigating the service system and talking to each other about how to understand developmental dynamics are really strongly associated with increased autism diagnoses," Bearman said. "The guess is that in wealthier neighborhoods, there are more opportunities for parents to be talking to each other at parks, schools, and other focal points."

According to the study, on average among children born between 1992 and 2000, a child from a poor family that lived in a more affluent neighborhood was close to 250% more likely than a child from an equally disadvantaged family living in a poorer neighborhood to be diagnosed with autism.

The study also found that when autism cases were split by severity, a striking pattern was revealed -- less severe cases were disproportionately found in wealthier and more educated neighborhoods. Among kids born in 1992, the odds of children with less-severe symptoms being diagnosed was 90% higher if they lived in a wealthy neighborhood. By the end of the study, that percentage had decreased by half, to 45%.

"Less severe cases, the kids who are the highest functioning, can often slip underneath the diagnostic radar in less affluent communities where the diagnostic resources are not as established," Bearman said. "If you're less severe, you might not be diagnosed because you don't seem to have a profound disability -- so you're just thought to be a weird kid."

As for policy implications of the study, Bearman said it is very simple. "I think you would like to reduce health disparities," he said. "So, in order to reduce the health disparity -- or really the service disparity -- we would need to allocate more resources to increase ascertainment to get children into treatment."

While the study focuses on children from California, the authors expect somewhat more amplified socioeconomic effects on autism diagnoses in other parts of the United States. "Since California has a state-wide program dedicated to serving kids with developmental disorders, it is likely that the inequalities in autism diagnoses are greater in other states," King said.