Decline of society and all that...
Mark, and others...
"Has nobody though to explain bad behaviour on bad parenting and the decline of discipline throughout our society"
Social commentators have been telling us how society is collapsing since, well, since the earliest social commentators started talking garbage really. Ancient Greek writers certainly did it - in fact you can probably find cave paintings somewhere depicting how kids today are out of control. Every generation has those who think the world was perfect 30-50 years ago and the modern generation is running riot and society is collapsing and, oh god, it'll be anarchy!!
None of them have yet been right.
The main reason for ADHD increasing is increasing diagnosis of ADHD. Once we used to call children naughty, now we say they have ADHD. Little has changed - we have just decided that this is a diagnosable and treatable condition, though it really just represents an extreme on the continuum of normal behaviour.