I've just started reading Poetic Medicine: The Healing Art of Poem-Making by John Fox, and I'm loving it. While there's so much to say, perhaps I'll just quote the first paragraph from the first chapter.
"Poetry is a natural medicine; it is like a homeopathic tincture derived from the stuff of life itself--your experience. Poems distill experience into the essentials. Our personal experiences touch the common group we share with others. The exciting part of this process is that poetry used in this healing way helps people integrate the disparate, even fragmented parts of their life. Poetic essences of sound, metaphor, image, feeling and rhythm act as remedies that can elegantly strengthen our whole system--mental, physical, and spiritual."
This book is a true delight to read, and I highly recommend it!