My mother works as a special aide at schools for children with (generally) severe disabilities, and she'll often talk about work over the dinner table. Pair that with my fascination for mental pathology, and you get this blog post. 
Anyone remember when M was diagnosed as being Autistic? To some of you, it may have been forever ago; I just read Generation X like two months ago. Anyways, after running into that, I got kind of curious, and have been trying to keep track of mental problems the x-men have had over the years. Funny thing is, the people who seem to come across these afflictions the most are the telepaths (or at least have some sort of psychic abilities). In the Ultimate series, Jean was locked up after her telepathic gifts began to develop, and she started hearing other peoples' thoughts. I forget if that happens in the normal series or not, but it struck me as interesting that Xavier never went through the same thing. Emma Frost, however, had a similar experience at around the same age (as she revealed in Generation X; not sure if it's cannon, as her past keeps getting re-done); in her case, it served to strengthen her willpower, herself stating that she's never been bent to another's will since (not sure if this is correct...). But with Jean, this experience is traumatic and haunts her even as she becomes an adult. You could attribute the differences to the families of both women; Emma Frost's family being cold and unloving, while Jean's family was warm and caring.
 And of course, most characters in the series have had breakdowns at one point, but that's not really what I mean. 
Actually, now that I think about it, M's diagnosis is interesting in that it marks a historically significant period in psychology, during which people were just beginning to learn about autism and other psychoses on the autistic spectrum. Wow, I hadn't noticed that till just now...
I wonder if it would be difficult, being a telepath (as M is, somewhat) and having such a different way of perceiving things. Given, it was the twins, not M herself, so it's kind of moot. Still, I'm keeping my eye open for anything that pops up.

You surprise me that you missed Legion.  Originally his multiple personality disorder was a means to focus his powers in different directions, yet his main personality was childlike.  As such, he needed constant care & attention... so he was pretty much shunned to the sidelines on Muir Island where he could be forgotten about.  And again... he had telepathic based abilities.

Anyone realize how Spider-man has to make jokes in life-threatening situations to manage the stress? His difficulty managing his different lives and his near manic sense of humor are classic ADHD symptoms.

And what about Deadpool?

@tommy_x: Deadpool isn't mentally ill, he's just aware that this is all a story, written by some asshole at a type-writer.

@mrburrows: And that's not a sign of mental illness?

On a side note, his brain is constantly breaking apart and reforming (depending on what series you're reading, this is mentioned once in a while), so you could say he has an illness literally of the brain..

@tommy_x: Honey, Deadpool isn't a member of the X-men

@squares: Well, that's a little debatable... At least he has now been a member of the X-Force if nothing else an he does run into x-Men every once in a while so I categorize him as an honorary X-Men or whatever. After all all the Utopian mutants were supposedly X-Men so if one counts them then why not count Deadpool as well? And he's been member in some alt realities too.