Is it big pharma pushing doctors to prescribe more? Is it doctors too lazy/busy to do a proper diagnosis? Is it mothers, fathers and teachers who seek to explain bad behavior and poor discipline (which is largely their fault) on medical conditions? Is it our foods which have changed over to GMO based content over the same period of time?
The basic cause of this is simple: lack of physical activity causes kids to be fidgety. They can't concentrate. Kids that fidget in class are disruptive. They are marked as "trouble".
Crap. My son was diagnosed in the early 90's. We resisted the diagnosis at first, then balked at medication. In the end, the medications did help him succeed in school and at such activities as soccer, where the difference in his ability to pay attention was easiest to observe.
The counter-intuitive thing about ADHD medications is that they are typically stimulants, hardly something you would think of giving to a hyper-active child. Our doctor described the symptoms as something more akin to the restlessness that can come with drowsiness than an over-active mind or metabolism.
Maybe some parents diagnose and treat to make life easier, but I'm here to tell you that we specifically did not medicate my son during weekends and vacations, partly to minimize the medication, and partly to be able to observe his baseline behavior to see whether it changed over time.
As for teachers, my wife has taught first and second grade for about 20 years, and in her school system, teachers are prohibited from offering a diagnosis or even acknowledging the possibility when asked; that is the domain of medical professionals, not teachers. YMMV, of course.
All that said, ADHD is certainly over-diagnosed, and that was almost certainly the case back when my son was diagnosed, at the early end of the chart in TFA. I have to say I was shocked at how much more prevalent the diagnosis has become. I tend to lay the blame at the feet of Big Pharma marketing treatments to lay people; the lengths they go to in advertising in magazines (with pages of fine print that few read or understand) and television, carefully staying within the guidelines of regulations (that clearly aren't helping) is absurd.