Originally Posted by
Aimless
And, just so we're clear, these relative age effects can go both ways. It may be so that many of the youngest kids are overdiagnosed, but in theory it may also be the case that some of the older kids are being underdiagnosed because, compared to their younger and more disruptive classmates, they seem pretty normal. I don't really believe that to be the case (except possibly in the sense that diagnosis is delayed by a few years so that you can see what's what), but in principle. You see similar things in the case of mood disorders, eg. depressive disorders, where gender and age matter greatly for getting an appropriate diagnoses. Some people are overdiagnosed, but very many more are underdiagnosed.