One in 10 of them may or may not have a gene also found in vast numbers of other people? What, that's it? Well, yes, of course it is.
Attention Deficit Hyperactivity Disorder does not exist. Mostly for being born boys rather than the girls wanted and expected by their mothers (more and more of whom in any case know little or nothing about men or boys), half a million British children are now drugged up to their eyeballs with Ritalin and such like as "treatment" for ADHD and various other nonexistent conditions.
Having long since decided that femaleness, simply in itself, was a medicable condition requiring the pumping of women's and girls' bodies full of highly poisonous substances in order to stop those bodies from doing what they do naturally, we now seem to have decided to treat maleness in the same way, and to get in even younger than we did with femaleness.
Meanwhile, prisoners are to be tested routinely for ADHD, if that is not already happening. Criminal behaviour is to be, or is being, defined as a manifestation of ADHD. Why else bother testing prisoners, in particular and as such, for it? So they will all be found to have it. But they don't have it. No one has it. It does not exist.