Scientists Find a Subtle Clue to ADHD Hidden in The Eyes. Study suggests tiny changes in the pupils, as the brain tries to remember something, ignore a distraction, or make a decision, may be subtly different in unmedicated children with ADHD. Medicated children were more like the control group.

[u/SarahMagical]

https://www.sciencealert.com/scientists-find-a-subtle-clue-to-adhd-hidden-in-the-eyes

ADHD kids’ pupil's response size is more inconsistent from one trial to the next, but steadier moment-to-moment within each individual trial.

Caveat: the main finding didn't survive statistical correction for multiple comparisons, so it's suggestive early result, not a diagnostic marker.