ADHD is not the result of bad parenting!
However I would say some poor parenting/attachment difficulties/ behavioural problems leads to families seeking a diagnosis of ADHD or ASD to explain the difficulties, as addressing the real difficulty is likely to be painful.
This 100%!
One of my children does have ADHD. He's textbook and we've known since he was age 2 ish. Other child is neurotypical. However, ADHD child is not naughty, is well spoken, polite and kind. Medication is literally life changing and whilst he's on his meds he's just like his sister - when he's coming off them, he can be scatty, loud, disorganised, emotional, melt downing over nothing etc etc. Literally like a switch isn't being controlled in his head. His paed is delighted with his progress on his mediation, as are school as he can now focus. His work is now coming on leaps and bounds.
I have a 'friend' who simply has a badly behaved child. Swears. No respect for anything or anyone. Honestly, nothing that a decent dose of decent parenting wouldn't sort out. He's a badly behaved, entitled little so and so. She won't hear a word of it (not one other place thinks he has ADHD, she's adamant he simply is 'masking' ) and is pushing and pushing for an ADHD diagnosis. NHS have said he doesn't have it. She's now paying to get that diagnosis.
I asked my paed about this and tbh she said it's becoming quite common.
However, whilst the ADHD medication works amazingly on my child as he does have ADHD, it will simply have the opposite effect on someone who doesn't have it.
So she said the parents will find out the hard way.