Resources for Diagnosis Have Contributed to Increased Autism Prevalence

Wealthy neighborhoods with more resources to diagnose autism have helped fuel the dramatic rise in autism prevalence, which has increased nearly 10-fold over the past 40 years. However, the influence of neighborhood wealth on diagnosis is beginning to fade.

A child living in a wealthy neighborhood is two and a half times more likely to receive an autism diagnosis than the same statistical child with the same level of parental support living in a poorer neighborhood, according to a study by sociologists Marissa King of the Yale School of Management and Peter Bearman of Columbia University.

"The amount of resources available in a community for making an autism diagnosis explains a lot of the increase in prevalence," said King. "Parents' education and economic status is important, but independent of their individual characteristics, the type of neighborhood they live in really matters for diagnosis."

Using data from the birth and autism diagnosis records for the roughly five million children born in California from 1992 through 2000, the researchers studied the characteristics of individuals and communities associated with the likelihood of an autism diagnosis, examining how they varied over time with prevalence rates.

Many individual factors, such as low birth weight, being male, and parents with more education, increased the risk for autism. However, these risk factors remained consistently important for diagnosis over time, and therefore did not contribute to the increased prevalence.

The researchers mapped the median property values of the neighborhoods in which children were born against autism prevalence. Neighborhoods where property values are higher and where residents are more educated were associated with greater autism prevalence, regardless of an individual's education or wealth.

The data show that neighborhood wealth matters most for diagnosis when prevalence rates are rising, such as in the early years of the autism epidemic when diagnosis was more costly and required specialized knowledge. Today, the influence of neighborhood wealth has weakened for children born to wealthy and middle class parents as diagnosis has become more common among these groups. However, the importance of neighborhood resources persists for children born to parents with fewer economic resources.

"A diagnosis is critical to treatment, so it is imperative that the disparities in resources available for autism be addressed," said King.

"Socioeconomic Status and the Increased Prevalence of Autism in California" (pdf) is published in the April 2011 issue of the American Sociological Review.