Like gp, I was also "almost" diagnosed ADHD as a kid, but my physician decided against it on the grounds that I was "too smart"; ADHD symptoms make kids do badly in school. But as school got harder, my performance did eventually slip terribly. I didn't need a diagnosis to "stick to me" -- the symptoms did that all by themselves. Depression set in, because there was no explanation for my behavior other than me being a shitty, lazy person with no "common sense" who was often admonished to just "stop being an idiot." But that's the dividing line between an illness and a mere maturity issue -- I *wanted* to do well. I was not consistently able to, in spite of an unwavering, categorically declared willingness to do so.
The real idiots are those who see only see one side of the "overdiagnosis problem" -- really, it's just a "diagnosis problem." Other than denialism, do these people have a solution to the difficulty in making the right call? Which side of caution do we want to err on?
Yeah, SSRI effects can be nasty. In my particular case, they have never approached anything resembling the nastiness of depression. Another anecdote - I don't personally know anyone whose life has been ruined by an unneeded Ritalin or SSRI prescription, but I have known many people whose lives have been turned upside down (in some cases, completely ruined) by an acute outburst of a previously undiagnosed mental illness.