This marks a 23% increase since the last report in 2009 and a 78% increase since CDC's first report in 2007. Some of the increase is due to the way children are identified, diagnosed and served in their local communities, although exactly how much is due to these factors in unknown.
The number of children identified with ASDs varied widely across the 14 Autism and Developmental Disabilities Monitoring (ADDM) Network sites, from 1 in 47 (21.2 per 1,000) to 1 in 210 (4.8 per 1,000).
ASDs are almost 5 times more common among boys (1 in 54) than among girls (1 in 252).
The largest increases over time were among Hispanic children (110%) and black children (91%). Some of this increase is probably due to greater awareness and better identification among these groups. However, this finding explains only part of the increase over time, as more children are being identified in all groups.
There were increases over time among children without intellectual disability (those having IQ scores above 70), although there were also increases in the estimated prevalence of ASDs at all levels of intellectual ability.
More children are being diagnosed at earlier ages—a growing number of them by age 3. Still, most children are not diagnosed until after they reach age 4, even though early identification and intervention can help a child access services and learn new skills.