STEP Study: Largest Randomized Prayer Trial Finds No Benefit — and a Backfire Effect

The Study of the Therapeutic Effects of Intercessory Prayer — known as STEP — enrolled 1,802 cardiac bypass surgery patients across six US hospitals between 1998 and 2000. Harvard cardiologist Herbert Benson led the study; the Templeton Foundation was a partial funder with institutional incentives to hope for a positive result.

Patients were assigned to one of three groups: receive prayer without knowing it, receive no prayer without knowing it, or receive prayer and be told so. Three established Christian prayer groups interceded on behalf of those assigned to receive prayer, beginning the night before surgery and continuing for two weeks. The outcome measure was any major complication or death within 30 days.

The results were published in the American Heart Journal in April 2006. There was no statistically significant difference between the prayed-for (unaware) group and the not-prayed-for group. The group told they were being prayed for had a slightly higher complication rate — 59% compared to 51-52% in the other groups — an effect researchers attributed to the psychological burden of knowing strangers were interceding on their behalf.

The trial's partial funder had every reason to want a positive result. It did not get one. The null finding has not been overturned by any subsequent study. It remains the largest randomized controlled trial of therapeutic intercessory prayer ever conducted.