Since when are advertisements allowed here? This is a pitch for a book (a fraudulent one at that).
Yes, ADHD is probably over-diagnosed and a lot of “oppositional behavior” would respond better to discipline - particularly if caught early on. Nonetheless, stating there are no legit psychiatric diagnoses, ignoring schizophrenia, bipolar disorder, and the like is so far off base as to be laughable.
Any psychiatric diagnosis is a behavioral diagnosis. It’s a person with “abnormal” behavior, meaning the person doesn’t behave like the rest of society.
There are no physical tests for these diagnoses, like there are for, say, epilepsy and brain tumors.
The history of psychiatry reads like a history in behavioral control. It should scare most people silly.