What % of children are admitted to Stanford? A sliver. What % of Stanford undergraduates make it to a "big law" firm? A small percentage.
The speculative point is that US men from UMC households who were admitted to elite schools and who subsequently went on to competitive jobs have higher Adderall abuse rates than you might expect. No, you can't find statistics on it. And to make the matter more difficult, they'll lie to your face about the subject.
This conjecture isn't even controversial, this notion is echoed throughout the broader culture. For example, see the following article from the New Yorker -- a magazine that caters to the families of these types: https://www.newyorker.com/magazine/2009/04/27/brain-gain . The article begins with the sentence, "A young man I’ll call Alex recently graduated from Harvard."
That is not addreal statistic, but adhd in kids statistic.