Reclassification May Be Responsible For The Increase In Autism, Experts Warn
In the news that failed to surprise anyone paying attention, a study from Penn State shows that nearly all the increase in Autism, across US in the first decade of the current century has resulted from reclassification. More particularly, it is the reclassification of children who showed intellectual disabilities as autistic.
Several decades since the introduction of autism as diagnosis, it has been reported by researchers that professional continue to engage in ‘diagnostic substitution’ moving people across different diagnostic categories like language impairment, mental retardation etc. to autism. For example, in a recent study, researchers from ULCA reexamined 489 children who were living since 1980 in Utah. The initial results from the study reported in 1990 found that 108 kids from this group who had received the “challenged” classification which in today’s parlance is “intellectually disabled” but not considered autistic. When the researchers returned to apply the diagnostic criteria for autism as existing today for the same group of 108 children, they noticed that 64 of those children could have been classified under autism together with the diagnosis for intellectual disability.
Adding to the evidence on this shift is a study by Dorothy Bishop and colleagues on re-evaluation of adults who were diagnosed during childhood as affected by developmental language disorder, as opposed to autism. Using 2 diagnostic tools for their evaluation today, Bishop and her colleagues noted that one fifth of these adults fulfilled the criteria laid down for autism spectrum although they were not recognized as autistic previously.
In this latest study at Penn by Santosh Girirajan and his colleagues, data pertaining to special education enrollment for 6.2 million children were evaluated. While the numbers were nearly stable for 11 years, diagnostic categories did shift around with increase in autism diagnoses nearly balancing the decrease in number of students categorized under ‘intellectually disabled’. At least 65% of the numbers were on account of this shift.
The numbers further were also dependent on the age. In comparison to the younger groups, older age groups showed a higher rate of shift and therefore, this shift in categories explained some 59% increase in autism in 8 year old kids and nearly 97% in kids older than 15 years.
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