There's way too many people who claim they have mental issues for all of them to actually have a serious one. I had a psychiatrist diagnose me with anxiety disorder, but I've seen at least three people who had variations or supposedly the same thing who acted completely differently (my sister, mostly functional just very specific about how she does things, a security guard who is very friendly but acts a bit off, and some woman at my hospital who locked herself in the bathroom for hours and panicked if you tried talking to her and also tried grooming/cleaned her genitalia in another bathroom later on). 

Another psychiatrist told me the opposite, which was a year later so a lot had changed, changing the diagnosis. I was also diagnosed with ADHD and depression at one point, the first was diagnosed when I was a hyper child and the other because I was a teenager. I think many people here are probably misdiagnosed due to age. Besides that, I don't buy the theory that roleplaying attracts people looking for an escape from reality. There's plenty of people here who legitimately like writing and don't absorb themselves into characters. Are actors also trying to escape from reality? People who play DnD? It's too simple of an explanation.

God forbid anyone actually enjoy writing characters and stories. That would be too positive.