JW - I think the 'causes' of the symptoms shown by children who are labelled ADHD are many and varied. There is no one cause, and there will never be concencus between experts on this.
I agree that many intelligent and questioning children would now be labelled ADHD simply because they don't fit comfortably into a system that often demands conformity. Drugs such as Ritalin give a quick fix for the adults dealing with the child - in my experience not always the teachers, I have known teachers battle with parents and medical 'experts' about children being given these drugs, but to no avail because the parent prefers the child to take the prescription. I have also known children who have been taken off Ritalin within weeks of being in a classroom where the teacher understands how children learn and teaches appropriately. (or 'facilitates learning' for those who don't like the word 'teach')
But it is not just the intelligent questioning child who gets diagnosed as ADHD, that is too simplistic. There are others who have a range of influencing factors that lead them to present challenging behaviours.
It is fascinating that brain imaging is showing a difference in the brains of ADHDdiagnosed children, with smaller parts of the brain that are thought to deal with attention and motivation. The question is, are these brain differences due to a genetic difference, or because those parts of the brain fail to develop through lack of use? Lack of use could be for a myriad of reasons, lack of play being one of them. You could add to the list the increased use of technology, games that demand quick response and no concentrated thought, lack of attention from adults, emotional abuse or neglect, alcoholism or drug abuse in the family, lack of positive role modelling, schools that demand long periods of sitting and no reprieve, inappropriate content taught at school..... the list could go on.......
I don't think the experts will ever agree, but I can't believe that the problem lies entirely with a generation of child and not with society. Certainly, many children display the symptoms of ADHD, but the question should be 'why is this the case?', not 'what drug can we give to surpress the symptoms?'
Having said this, there needs to be help available for those adults who deal with children who have ADHD type symptoms. But of course, drugs are cheaper for health authorities than real intervention, and also make a lot of money for the drug companies.