Armchair diagnosis is dangerous IMO. It can be a form of gaslighting. Sure everyone can benefit from therapy, meditation and improving systems for managing sadness, frustration, impatience but telling yourself or someone else you have ADD, compulsive disorder, anxiety is a great way to pop the self esteem bubble and confidence you need to get through life.
In the workplace it's especial dangerous; you can force someone to question why they don't like a job or feel isolated or bullied by convincing them their perception is really the problem.
It doesn't take much effort to convince someone who is upset by circumstance that they have a problem. "You're too sensitive" "you're depressed" "that person has an anxiety problem" when really the environment at the job might really be the problem or some basic coaching might be the solution.
I worked somewhere in which people openly admitted the company culture drove them to therapy yet were so "grateful" for an "open and inclusive" environment. The cognitive dissonance there was very disturbing.
This occurs in families as well. I grew up in an abusive household and, well damn, your parents will do their best to convince you that you are the crazy one and need help.