Annoyingly the same old bollocks gets spouted whenever this topic comes up.
Whilst I'm sure there are parents who claim their genuinely nasty little sh!ts are really nice kids who just suffer from an attention disorder the reality is that most kids labelled with the disorder, and their parents, wish it weren't so. ADHD isn't a disease or an excuse it's a genuine disorder diagnosed in about 3% - 6% of Western kids and about 2% of children worldwide, it isn't simply 'being naughty' or disobedient although that is often how it is viewed by some when judgementally viewed from afar. I accept that in times gone by those kids would just have been known as naughty kids, we all remember them from school, they probably wouldn't have amounted to much in life and many would have left school with nothing, but that was in the days when it was acceptable to smoke in the same room as your toddlers, drive a car when you were pissed, wear flares and eat lashings of lard and salt because they were considered good for you, the world has moved on thankfully.
ADHD is a term used to describe a set of symptoms all centred around a short attention span and inability to sit still for more than five minutes, it is normally most obviously present in childhood. I am not the sort of parent to label my kids with any name other than 'little bastards' but when his teacher insisted my son went to see the doctor and the doctor said how the hell have you coped with this all this time - he was 14, it made me do some research, speak to some medical professionals and find out just what was going on. My son never slept for more than 4 hours a night as a child, ever! We just thought he was 'naughty' but that is but one symptom of the disorder, a symptom that now he is 23 he still carries, fortunately it is probably the only symptom of any significance that he can't manage, other than the fact he still can't sit still for more than 5 minutes and is easily bored - aren't we all. The symptoms are outwardly less obvious as an adult and obviously they do tend to diminish with age and the reduction of galloping hormones and boundless energy we associate with childhood.
Without ritalin, - evil drug from hell if you believe the hype, and medical/ psychological guidance he would never have achieved his 11 GCSE's grade A* to C, not because he was thick, or naughty but simply because for the two years he took the drug he was able to learn how to manage his symptoms and control his constant urge to move on and do something else less tedious.
Now, the 'label' is a small price to pay to ensure your kids aren't simply sidelined as naughty little bastards and are able to get as good a start in life as other less challenged kids, so when the ignorant, ill informed or shit stirring start their rant you'll understand why parents like me simply raise our eye brows and sigh.
With regards to joining up, as I understand it the disorder isn't so much of an issue as long as it isn't associated with a troubled past and constant brushes with the law - think about it, couldn't the mob do with a few more people who spend less time in their pit, are often fitness obsessed and like to be doing something constructive rather than sitting on their arse playing computer games, it's the medication often associated with it that restricts entry and I believe 3 years drug free is enough for consideration to be given to join nowadays but I'm sure one of the career/ medical guys can clarify that.