Honestly, I know of somebody who's on DLA because of ADHD. After talking to him a few times he's implicitly stated that it's too easy to get DLA, because of ADHD, and that he "lied about it" for the most part to get money from the government. He was eventually reported for benefit fraud, by one of his family members if I remember correctly... the best part is, after being assessed he was still allowed to continue receiving DLA.
Which either leads me to believe he's either lying about lying. Or he's lying to the DWP. Either way, he's a bit of a tool for doing it. And he doesn't help this entire situation at all, there are people who have ADHD and it seriously affects their lifestyles... What also doesn't help sufferers of ADHD, is the fact that it's one of the most commonly misdiagnosed disorders on the planet. And we'd be naive to think there are no people out there looking to abuse the system to get an easy life.
But anyway... a little more education on the effects of ADHD are required it seems, as people are quick to dismiss an over-active child, or a dismissive one (who's not being challenged enough, let's say) as having AD(H)D. And some people don't believe it exists at all and are willing to bet it's just an excuse for a child to be naughty... It's completely black and white for some people, it's mind boggling.
I realise that may have gone off on a tangent, concerning the nature of the original post... but meh, had a little bit to say on the subject it seems!