The Difference Faith Makes - Clinical Studies
The following are studies that demonstrate the beneficial power of faith in God:

Study sample: 5-year follow-up of 2,025
residents of Marin County who were 55 years
and older.
Study results: “For each sex, male and female, weekly (church) attendees had the lowest mortality and non-attendees had the highest mortality.”

Oman D, Reed D. Religion and mortality among the community-dwelling elderly. Am J Public Health 1998; 88(10):1469-1475.

Study sample: 400 community residents age 65 and older.
Study results: Risk of diastolic hypertension
(high-blood pressure) reduced up to 40% for: regular (church) attendees who also prayed or
read the Bible daily.

Koenig HG, et al. The relationship between religious activities and blood pressure in older adults. Int J Psychiatry Med 1998; 28(2):189-213.

Study sample: 542 patients 60 or older; consecutive admissions to Duke University Medical Center.
Study results:
Regular church attendees were 43% less likely
to have been hospitalized during previous year.

If hospitalized, briefer stays -- non-church
affiliated spent 25 days in hospital; church
affiliated spent 11 days.

Koenig HG, Larson DB. Use of hospital services, religious attendance, and religious affiliation.
South Med J 1998;91(10):925-32.

Study sample: Nearly 600 severely ill hospitalized patients aged 55 and over.
Study results: Spiritual coping via connection with God and receiving religious support resulted in:

Less depression
Better quality of life
Greater compliance with care

Koenig, HG, et al. Religious coping and health status in medically ill hospitalized older adults. J Nerv Ment Dis 1998;186(9):513-21.

Twelve other studies published since 1980 found persons in organized religious activity had higher levels of life satisfaction.

Final quote from summary of the clinical studies:

Nothing in life is more wonderful than faith -- the one great moving force which (as it turns out) we can weigh in the balance and test in the crucible not so mysterious, and not so indefinable, known by its clinical effects, faith pours out an unfailing stream of energy while abating little of its potency.