Wrong, one cannot make a diagnosis either way without one on one consultation and assessment.
I think sometimes you can form a valid opinion about something without necessarily having to be a qualified expert. If your car makes noises like someone attacking sheet metal with a chainsaw, you don’t have to be a mechanic to conclude that there is probably something wrong with the engine.
If someone tells you he thinks he smells smoke, and it might be prudent to leave the building, are you going to wait for a qualified fire chief to give you permission?
Not when it comes to conditions of the mind and medicine in general.