Penn State University researchers warn that the increasing autism prevalence may be due to inappropriate terminology and not an actual rise in cases. The number of autistic children, they say, has increased not because of a rise in cases, but because of the diagnostic procedure blur that doctors are faced with.
The study itself has surprised no one who was actually paying attention. What Penn State scientists suggest is that the majority of autism cases diagnosed in the US (which have increased three-fold) are the result of reclassification. What has happened is that massive numbers of children with intellectual disabilities were wrongly diagnosed as being autistic.
Granted, researchers note that there is an overlap between autism and the number of different neurobiological conditions. Moreover, the diagnostic criteria for autism diagnosis have also broadened.
But even so, the massive increase is evident. Back in 1975, the overall prevalence of autism was 1 in 5,000. In 2002, that number rose to 1 in 150 children. In 2012, that number reached 1 in 68. So medical experts can’t fail to wonder whether there isn’t anything wrong with the diagnostic procedure itself.
Autism is a particularly difficult condition to diagnose, for one, because of the multitude of clinical features that patients display. More importantly, each individual may show only some features or certain combinations of features, making matters more difficult.
The Penn State University Study was led by Santhosh Girirajan and examined the enrollment data of more than 6.2 million children who had been enrolled in special education facilities. What the scientists observed was that, while the numbers remained relatively stable for over a decade, there were shifts in diagnostic categories.
Basically, they observed a massive increase in autism diagnoses among the children whose enrollment data they examined. But that massive increase, researchers noticed, was balanced out by a corresponding decrease in the number of intellectual disability diagnoses. This shift, the Penn State University researchers said, amounted to almost two thirds of the numbers.
In total, 65 percent of the increase in autism-diagnosed children between 2000 and 2010 was attributable to the shift of diagnoses from intellectual disability to autism. But what’s worse is that, the older the children wore, the higher the reassignment percentage was. Consequently, for children aged 9, the total rise in autism was 59 percent, while among children aged 15 and over, reclassification was responsible for 97 percent of the increase.
Such studies will hopefully fuel further research aimed at correctly examining the prevalence of autism. Furthermore, diagnostic measures should be revised and incorporate not only rigorous follow-up but also detailed genetic analysis.