It's yet another piece of evidence that ADHD is a developmental disorder, it develops over time, and those who are younger have brains which are underdeveloped.

It's yet another piece of evidence that ADHD is a developmental disorder, it develops over time, and those who are younger have brains which are underdeveloped. Their ability to tamp down disruptive behaviors and use executive functioning to effectively manage planning is reduced compared to other children. So, in younger children, those who are borderline ADHD will appear to be more solidly ADHD, and those with moderate or severe ADHD will seem to have worse symptoms, as we're putting them in a classroom and comparing them with children whose brains have a higher EF capacity. It's also worthwhile to note that the gold standard diagnosis of ADHD involves observation of childrens' behavior in the classroom, where they will be compared to older, more neuro-developed classmates.