TUESDAY, Nov. 4, 2014 (HealthDay News) -- The dramatic increase in the number of children diagnosed with an autism spectrum disorder is largely the result of changes in how the condition is reported, Danish researchers contend. The report was published online Nov. 3 in JAMA Pediatrics.
At least in Denmark, the researchers say, most of the increase -- 60 percent -- can be attributed to changes in diagnostic criteria and the inclusion of out-of-hospital diagnoses. For the study, the researchers collected data on 677,915 children born in Denmark from 1980 through 1991. These children were followed from birth until autism was diagnosed, or until they died or emigrated, or until the end of 2011, whichever came first.
From this group, 3,956 children were diagnosed with an autism spectrum disorder. Most were diagnosed after 1995, after changes in the diagnostic criteria and inclusion of outpatient diagnoses occurred, the researchers found. These findings should provide some relief for parents who've worried that the increase in numbers was caused solely by more children actually developing the disorder.
"That the increase until now has been left more or less unexplained has undoubtedly raised considerable concern among the public and might, in fact, have affected some parents' health decisions regarding their child," lead researcher Stefan Hansen, from the section for biostatistics in the department of public health at Aarhus University, told HealthDay. "As our study shows, much of the increase can be attributed to the redefinition of what autism is and which diagnoses are reported," Hansen said. "The increase in the observed autism prevalence is not due alone to environmental factors that we have not yet discovered."