A substantive amendment to this systematic review was last made on 31 January 2000. Cochrane reviews are regularly checked and updated if necessary.
Background: Prayer is an ancient and widely used intervention for alleviating illness and promoting good health. This review focuses specifically on intercessory prayer, which is organised, regular and committed, and those who practise it will almost inevitably hold some committed belief that they are praying to God. Whilst the outcomes of trials of prayer cannot be interpreted as 'proof/disproof' of God's response to those praying, there may be an effect of prayer not dependent on divine intervention. This may be quantifiable, making this investigation of a most widely used health care intervention both possible and important.
Objectives: To review the effectiveness of prayer as an additional intervention for those with health problems already receiving standard medical care.
Search strategy: ATLA (1949-1997), Biological Abstracts (1985-1999), CINAHL (1982-1999), The Cochrane Schizophrenia Group's Register (December 1999), CCTR of the Cochrane Library (Issue 4, 1999), EMBASE (1980-1999), MEDLINE (1966-1999) and PsycLIT (1887-1999), Sociofile (1974-1996) and Sociological Abstracts (1963-1999) were methodically searched. All references of articles selected were searched for further relevant trials.
Selection criteria: Randomised trials of personal, focused, committed and organised intercessory prayer on behalf of anyone with a health problem were considered. Outcomes such as achievement of desired goals, death, illness, quality of life and well-being for the recipients of prayer, those praying and the care-givers were sought.
Data collection and analysis: Studies were reliably selected and assessed for methodological quality. Data were extracted by two reviewers working independently. Dichotomous data were analysed on an intention-to-treat basis.
Main results: There was no evidence that prayer affected the numbers of people dying from leukaemia or heart disease (OR 1.11, CI 0.79-1.56, n=1424). Intercessory prayer did not clearly decrease the odds of people with heart problems experiencing a bad or intermediate outcome (OR 0.8, CI 0.64-1.00, n=1444) but this finding was moved towards the null by inclusion of a negative assumption for those who were dropped from the analysis in one study. Prayer increased the odds of readmission to the Coronary Care Unit (OR 1.54 CI 1.02-2.33, n=1406) but these results are made significantly negative by the inclusion of an assumption of poor outcome for those not accounted for in the final analyses.
Reviewers' conclusions: Data in this review are too inconclusive to guide those wishing to uphold or refute the effect of intercessory prayer on health care outcomes. In the light of the best available data, there are no grounds to change current practices. There are few completed trials of the value of intercessory prayer, and the evidence presented so far is interesting enough to justify further study. If prayer is seen as a human endeavour it may or may not be beneficial, and further trials could uncover this. It could be the case that any effects are due to elements beyond present scientific understanding that will, in time, be understood. If any benefit derives from God's response to prayer it may be beyond any such trials to prove or disprove.
