I'm not sure that the term "mental illness" is pretty useful if your goal is to do change work. Part of the societal role of the term is to distinguish mental phenomena where it's legal to take drugs to solve them from mental phenomena where it isn't. To decide what insurance will pay for and where it won't pay. Those concerns dictate how wide or narrow we have our net as to what constitutes "mental illness".
If we talk about anxiety I'm not sure that "mental illness" is a good framing. Every healthy human being sometimes has anxiety. There might be some brain damage that prevents certain people from having anxiety, but it's part of normal human functioning.
That means it's useful to learn how to deal with anxiety in a productive fashion. There are a bunch of emotional management skills that are useful for everyone.
I know little about schizophrenia but my general impression is that it's something that's qualitatively very different from a phobia.
Anxiety transcends a normal thing and enters mental illness when it becomes pervasive and unreasonable. My anxiety about having used a wrong word in a conversation I had last year is unreasonable. My constant feeling of dread is unreasonable because I'm not constantly in a situation that should inspire dread. Mental illness is really hard to define properly- there always seems to be something left out, or something that's implied to be illness when it isn't.
Honestly, I feel like the discussion has been derailed a bit- we're focusing on defining a very vag...
For a site extremely focused on fixing bad thinking patterns, I've noticed a bizarre lack of discussion here. Considering the high correlation between intelligence and mental illness, you'd think it would be a bigger topic.
I personally suffer from Generalized Anxiety Disorder and a very tame panic disorder. Most of this is focused on financial and academic things, but I will also get panicky about social interaction, responsibilities, and things that happened in the past that seriously shouldn't bother me. I have an almost amusing response to anxiety that is basically my brain panicking and telling me to go hide under my desk.
I know lukeprog and Alicorn managed to fight off a good deal of their issues in this area and wrote up how, but I don't think enough has been done. They mostly dealt with depression. What about rational schizophrenics and phobics and bipolar people? It's difficult to find anxiety advice that goes beyond "do yoga while watching the sunrise!" Pop psych isn't very helpful. I think LessWrong could be. What's mental illness but a wrongness in the head?
Mental illness seems to be worse to intelligent people than your typical biases, honestly. Hiding under my desk is even less useful than, say, appealing to authority during an argument. At least the latter has the potential to be useful. I know it's limiting me, and starting cycles of avoidance, and so much more. And my mental illness isn't even that bad! Trying to be rational and successful when schizophrenic sounds like a Sisyphusian nightmare.
I'm not fighting my difficulties nearly well enough to feel qualified to author my own posts. Hearing from people who are managing is more likely to help. If nothing else, maybe a Rational Support Group would be a lot of fun.