That'd be the tl;dr if you actually didn't understand what that sentence said. Volume was lower in some subcortical regions. That's some parts of about a quarter of the brain.

The implied message behind your tl;dr is also missing the mark:"Most differences remained significant after adjusting for [...] intelligence quotient."

It's a bummer to see these kinds of non-thinking reddit laughlines on HN - this is actually an extremely interesting study. For a summary, I recommend the "Added Value of this study" section. One of the most interesting findings (to me, at least) is e.g. the fact that brain alterations extend well beyond emotional regulation even to temporal & motor capacities.

There are also interesting questions to pose - e.g. why the study only found ADHD in subjects with conduct disorder. (That's not an expected result in that sample size - while ADHD & CD can co-occur, ADHD without CD is significantly more common)

I think we can do better than cheap shots.