A few years ago, National Institute of Mental Health (that's NIMH, as in "Mrs. Frisbee and the Rats of...", my esteemed employer) sponsored a symphony concert called "Music and Mental Health", featuring work of great composers who most probably suffered from profound mental illnesses, mostly bipolar disorder (manic-depression). Works by Mahler, Chopin, Shubert, R. Strauss and others were included. Most of their works of genius were done during "manic" phases, followed by periods of deep depression. There are also large numbers of "troubled geniuses" in the visual arts, like Van Gogh.

It seems that an element of true creativity is the ability to steer your mind in directions that are outside the "norm" for whatever era you live in, but that is usually a two-edged sword. The very spirit and mental imagery that lets one create something truly new and beautiful also can make one's life painful when trying to cope with the world around you.

Creative people who turn to drugs may be using the drugs not to promote the creativity, but to deal with a world they don't fit into because of the creativity.

That said, "just being misunderstood doesn't make you an artist..." - too many musicians fall into the trap of thinking adopting the "tortured artist" role excuses their own abuses.