http://my.webmd.com/content/article/86/98933.htm

“April 26, 2004 — More than a third of Americans pray in hopes of achieving better health, according to a new study.

Researchers say prayer is a common practice in the U.S., but little is known about how people use it for health concerns. Although prayer has no proven effect, researchers say previous studies have shown a positive association between spirituality and better health…”