ADHD is Neither a Disease or a Disorder
We should be clear from the start that having a disease or a disorder means one has an objective physical abnormality. The first obligation of all physicians is that of diagnosis. The first question posed by the duty to diagnose is: Is there a physical abnormality—gross (a visible or palpable lump), microscopic (cancer cells of biopsy or ‘Pap’ smear), or chemical (as in diabetes, gout, phenylketonuria), yes or no? If “no,” there is no disease and the patient is medically, physically normal. It is this group, those with “no evidence of disease” (NED) from which all psychiatric and psychological patients derive. The public worldwide has been deceived and mislead for decades on this fundamental point that is well known to physicians. No patient with ADHD or with any psychological or psychiatric entity has an actual disease. Physicians telling them they do knowingly deceive them abrogate their right to informed consent, and drug normal individuals, that is, poison them. This is the standard of care in psychiatry today. NICE addresses the “disease” vs. “no disease,” physical vs. psychiatric issue stating, “the disorder remains one that is defined at a behavioral level, and its presence does not imply a neurological disease” (p. 17) [1]. Using the term “disorder” which is synonymous with disease, meaning “A disturbance of function, structure or both,” NICE sews the seeds of confusion that for decades has lead patients and the public worldwide to view ADHD and all psychiatric and psychological entities as diseases when they absolutely are not [2]. Having called ADHD a “disorder” NICE stated: “The diagnosis of ADHD does not imply a medical or neurological cause” (p. 29) [1]. Given that ADHD is not a disease or a disorder, it is not appropriate to speak of it’s possible medical or neurological causes. In medicine when no disease has been found the diagnosis is “no organic disease” (NOD), or “no evidence of disease” (NED), calling for no discussion of causation. To discuss cause where no disease exists is to further mislead and confuse.

Although the term 'Disorder' seems to be more or less used when describing psychological/behavioral problems and has been around for quite a while (Multiple Personality Disorder anyone?).
I do think ADHD is over-diagnosed. If I had gone to school in today's climate, I would have quickly been labeled ADHD and shipped off to the school councilor who would agree with the ADHD diagnosis and then refer me and my parents to a psychologist that the school and/or board supports who would just rubber stamp the teacher/councilors diagnosis and prescribe Ridilin or something. The school would then potentially force me to take this medication and potentially back it up with the threat of suspension/expulsion.
I may have been hyperactive as a kid, I may have disrupted classes and caused all sorts of trouble but I grew up into a healthy well adjusted adult without the need for pills. I suspect a good deal of these ADHD diagnosis results are so that parents can tell their sweet little precious child that theres nothing wrong with them its the fact the tests are biased against them or something or set them up for when they are in college/university so that they can do things like take their tests whenever they feel like and/or take as long as they want as these are restrictions that 'normal' students have to abide by but anyone with a recognized learning disability or physical disability is allowed to dispense of. At least in Canada (which is not too far behind America in ADHD overdiagnosis I believe)
Many ADHD kids don't need the pills. What they need is educated educators. Just because a kid learns differently than the majority, doesn't mean he can't learn. Our new prez is left handed. He signs laws differently, but he can still sign. Don't give him a pill, because you prefer to read only right handed signatures. Teachers that don't care to learn about kids that learn differently, don't like kids. That said, some kids do need the meds. But many don't, yet take them anyway. I blame that on the Rx companies, not the kids or the teachers. The Rx chick that calls on the doctor makes twice as much $ as the teacher.