I wonder if kids would still self diagnose after having witnessed first hand what those illnesses are like and what they do to someone you love.
There's no social capital to be gained by actually having the illness. Pretending you have it garners sympathy, elevates your voice, and ingratiates yourself into a community of like-minded people (most of whom also don't have the illness).
He was asked if he was shown proof that would change his mind could he and he said he couldn't, because his entire identity was built around this belief. If he changed his mind he would lose everything.
This is one of the dangerous things about echo chambers and micro communities produced by social media, it gives people a global identity even if their identity is based on nonsense.