Okay, was just talking to @vivithefolle, and here’s another point in the “Ron has ADHD” column.
Ron’s overreactions to perceived rejections and betrayals (by Harry and Hermione in books 4 and 6, and also the way the locket was able to really get its hooks in him) read a lot like Rejection-Sensitive Dysphoria.
Please consider how quickly Ron spiraled from “Hermione kissed Krum” to “Hermione could never love me because I am a worthless nothing who can’t possibly compare.”
Does not mesh well with Harry, who’s prepared to write off relationships before he can get hurt, or Hermione, who’s constantly afraid she doesn’t really have friends who actually like her. By the time Ron’s brain chemicals have chilled out a little, Harry or Hermione have gone into Fighting With Ron mode. And also “go away and get myself under control” is actually an incredibly grown up and intelligent strategy for dealing with RSD in all circumstances other than “the gang’s on the run and in hiding because Voldemort wants to kill us.”