The rates of autism among children enrolled in special education programs in the US have continuously increased by greater than three-fold from 2000-2010. According to a new study, the reason for such rise is said to be rooted from the new classification system, which aims to categorize individuals who previously would have been given the diagnosis of other intellectual impairment disorders.
Genetics had been linked to the increased risk of developing nosologically distinct conditions such as autism and epilepsy; however, the available statistical data pertaining to the prevalence of autism do not consider the effects of comorbidity of these conditions to the diagnosis of autism.
With this, researchers from Penn State analyzed the enrollment data of children in the US from 2000-2010. The information was obtained via the United States Individuals with Disabilities Education Act (IDEA) and the researchers were able to look at 11 years-worth of data from about 6.2 million children per year.
The findings of the study, published in the American Journal of Medical Genetics, show that the prevalence of autism among the special education community shot up by 331 percent from 2000-2010. The researchers said that this significant increase may potentially be due to a diagnostic reclassification from common comorbid characteristics such as intellectual disability (ID). Meanwhile, ID exhibited a drop in prevalence amounting to an average of about 64.2 percent of the increase of autism among children aged 3-18 years old. Higher proportions (75 percent) of older children were observed to undergo the transition from ID to autism compared to younger children (48 percent). Negative correlations pertaining to the prevalence of autism and ID varied from state-to-state, suggesting that distinct state health policies may be a significant factor in classifying autism.
"For quite some time, researchers have been struggling to sort disorders into categories based on observable clinical features, but it gets complicated with autism because every individual can show a different combination of features," says Santhosh Girirajan, lead author of the study and an assistant professor of biochemistry and molecular biology and of anthropology at Penn State. Complications start to arise in individuals who have multiple diagnoses because the clinical manifestations of autism are frequently noted in individuals with other neurological disorders.
