This thread has lots of misinformation.
ADHD is real today and it was real 100 years ago as well. There are many mental disorders, and like physical ones, one medication isn't a cure all. Medicine is said to be an art. It's not pure science. If a child experiences side effects that's a clue that that diagnosis or medication may be wrong — meaning it's time to adjust, not throw out the whole notion of diagnosis and treatment.
Most ADHD meds are similar to caffeine in that they will basically do nothing except reduce appetite unless a child actually has ADHD. If a child has a ADHD and the meds are right, it simply brings them back to "normal range".