Research on the health benefits of prayer has shown decidedly mixed results. When individuals pray in a ritualistic or rhythmic way, such as saying the rosary or repeating a mantra, they can lower their heart rate. In fact, one study showed that the cardiovascular effects of rhythmic prayer are similar to that of doing yoga. Studies on the effects of intercessory prayer — that is, prayer for other people — show less optimistic results. One study even showed that people who received intercessory prayer from other people were more likely to suffer post-surgery complications.
More about the health benefits of prayer:
One difficulty in doing studies on the health benefits of prayer is that people who might pray regularly might also follow religious restrictions on alcohol, smoking and drugs, thereby improving their overall health. It then becomes difficult to determine whether the prayer or lifestyle choices are more responsible for any health benefits.
One survey showed that one-third of Americans pray about their health.
Another study showed that people who pray regularly are less likely to exercise than non-prayers.