Counting Cases of Autism

The South Korean study showed a greater prevalence of autism than many other studies. At the American Journal of Psychiatry, Tony Charman writes:

One reason why counting autism is so difficult is that when you set a high threshold for who has autism, the count is lower, and when you set a low threshold, the count is higher. There is also some evidence that culture drift in our understanding of what constitutes autism has changed over the decades in ways that are hard to quantify and study.

...

The authors describe how they examined whether measured child and school factors, such as grade, sex, and school size, affected participation at each stage, and broadly they did not. However, there are a host of possible unmeasured factors that might have influenced participation in such a way as to introduce bias—in the direction of overestimating prevalence. These include school and parent knowledge and interest in participating in an autism study and parental concerns about their child's development and behavior.

...
A final intriguing and perhaps more hopeful point is made in Kim and colleagues' discussion of how it is that so many pupils with an (undiagnosed) ASD can apparently manage to be educated and integrated in mainstream classrooms. This is a useful reminder that developmental conditions such as autism are affected by the environment in which a child develops and that accommodations to such environments can sometimes have a positive impact on children with a "disorder."