USF College of Public Health researcher Russell Kirby, PhD, has contributed to two key studies with implications for the prevalence of autism spectrum disorder in the U.S. population. Both recently published studies were led by the Centers for Disease Control and Prevention’s National Center on Birth Defects and Disabilities and its Autism and Developmental Disabilities Monitoring (ADDM) Network.
Kirby, professor and Marrell Endowed Chair in the college’s Department of Community and Family Health, is an expert on developmental disabilities epidemiology and prevention as well as risk factors for poor pregnancy outcomes.
The first study co-authored by Kirby reported that new guidelines for autism spectrum disorder may reduce the number of U.S. children diagnosed with this group of developmental disorders that can cause language delays, impaired social and communication skills, and repetitive behaviors.
The population-based study was reported online Jan. 22 in advance of print, in the journal JAMA Psychiatry.
The researchers reviewed data from more than 6,500, 8-year-olds living in 14 U.S. regions participating in the ADDM Network. They found that 81 percent of the children classified with autism under the old version of the psychiatric manual (DSM-IV-TR) would be diagnosed with the condition under the newly revised manual (DSM-5) released last year.
There has been some concern voiced by parents and others that the new criteria would limit access to educational or social services for children previously diagnosed with autism.
“Almost all the children with complex presentations of autism meet the new case definition,” Kirby said.
He added that children who do not meet the criteria for a diagnosis of autism could be evaluated for other developmental delays and may qualify for services under another psychiatric diagnosis.
“It depends on the state,” Kirby said. “In some states, the child only needs to be identified as at risk for developmental delay to qualify for services, especially at under 3 years of age. Other states, like Florida, require a diagnosis before providing access to services.”
The second study co-authored by Kirby found that three perinatal risk factors – premature birth, small for gestational age (a fetus smaller than normal for the age of pregnancy), and Cesarean delivery – notably contribute (12 to 13 percent) to the risk of developing autism spectrum disorder in the U.S. population. However, a large proportion (87 percent) of the autism burden could not be attributed to the three risk factors analyzed. Other known risk factors for autism spectrum disorders include maternal and paternal age, and race/ethnic differences in prevalence have also been observed in the United States.
The study appeared online Jan. 15 in the journal Annals of Epidemiology.
“We know that the prevalence of autism has been rising over the last 20 to 30 years… but as this study shows, there are still a lot of unknowns about what causes the condition,” Kirby said. “We need more investigation of the interaction between possible genetic contributions and environmental risk factors.”
