The likelihood of a school-aged American child receiving a diagnosis of autism, Asperger syndrome or a related developmental disorder increased 72 percent in 2011-12 from 2007, according to an analysis of a phone survey of parents released Wednesday by the Centers for Disease Control and Prevention and the Health Resources and Services Administration.
According to experts not involved in the report, the increase coincided with a period of soaring awareness of autism spectrum disorders among clinicians and schools, as well as parents.
The report emphasized that while the numbers changed from 1 in 86 children, ages 6 to 17, having received a diagnosis in a 2007 parent survey, to 1 in 50 children in the current report, most of the increase was because of previously undiagnosed cases.
‘‘Our findings suggest that the increase in prevalence is due to improved recognition of autism spectrum disorders,’’ said Stephen J. Blumberg, a senior scientist with the centers’ National Center for Health Statistics and the lead author of the study, ‘‘as opposed to children with newly developed risks for them.’’
Parents in the newer survey who reported that their children had received a diagnosis between 2008 and 2012 were far more likely to report that the diagnosis had been characterized as ‘‘mild’’ than parents who received the diagnosis earlier.
‘‘We in the field don’t have a standard set of definitions about what is mild and severe yet,’’ said Dr. Susan L. Hyman, a professor of pediatrics at the University of Rochester Medical Center. ‘‘Yet this survey allows parents to determine whether they see their child as mild or severe.’’
In keeping with earlier studies about autism spectrum disorders, the new report reflected gender disparities. In the new study, 1 in 31 boys had received a diagnosis, up from 1 in 56 boys in 2007. By contrast, 1 in 143 girls received a diagnosis, according to the latest report; in 2007, 1 in 204 girls received a diagnosis.
The rise in diagnoses was also generally greater among 14- to 17-year-olds, underscoring the likelihood that these were previously unrecognized cases.
Nonetheless, with parents describing 1 in 50 children as having significant social or other challenges, the new data ‘‘tells us the real numbers of children needing help to experience social and academic success,’’ said Deborah A. Fein, a co-author of a forthcoming study in Pediatrics about a widely used screening tool for autism in toddlers. ‘‘We need to find ways of funding and providing help to these children,’’ Fein, a professor of psychology at the University of Connecticut, said in an email.
Experts also reacted cautiously to the new report because of its methodology, in which researchers randomly dialed landlines and cellphone numbers, interviewing parents.
By contrast, a study released last year by the CDC’s Autism and Developmental Disabilities Monitoring Network looked directly at school behavioral assessments and clinical reports of children who were 8 years old in 2008 and applied a standard checklist of criteria for the diagnoses. While that study found a 78 percent increase in autism spectrum disorders from 2002 to 2008, it said the likelihood of a child receiving such a diagnosis was 1 in 88.
Because the methodologies were so different, as well as the age range of the children themselves, it was difficult, experts said, to draw conclusions about prevalence or diagnoses, not least because clinicians themselves use different assessment tools. A diagnosis of an autism spectrum disorder can change as a child grows older.
Dr. Catherine Lord, director for the Center for Autism and the Developing Brain at NewYork-Presbyterian Hospital/Weill Cornell Medical Center, who was not involved in the CDC study, said, ‘‘We can’t dismiss this report, but we can’t interpret it to mean that more people have a diagnosis. It means that more families are thinking of this as a possibility and maybe more professionals are bringing it up.’’