The author concluded that the review findings about the effects of intercessory prayer were inconclusive. The author’s conclusion appears to reflect the differences between the studies, but poor reporting of the review methods makes it difficult to comment on its reliability.

To evaluate the effectiveness of intercessory prayer in clinical settings.

MEDLINE, PsycINFO and Social Work Abstracts were searched in July 2006 using the search term ‘prayer’. In addition, the reference lists of major reviews and other relevant studies were screened.

All studies that evaluated the efficacy of intercessory prayer in a population of clients or patients were eligible for inclusion. Studies were included whether or not participants knew they might be receiving prayer. Single-case studies, cross-sectional studies, studies in which there was non-random voluntary assignment to treatment groups, and studies evaluating other forms of distant healing were excluded.

All of the included studies were controlled studies. In all but one study the control groups received usual care. The primary studies involved patients with a wide variety of conditions, and studies assessed a wide variety of physical and psychological outcomes; the outcomes were poorly reported. The participants were of unknown religion or a wide range of religions. The interventions were carried out by persons of a wide variety of religions. Where reported, the duration of the interventions ranged from 3 days to 15 months.

The author did not state how the papers were selected for the review, or how many reviewers performed the selection.

The author did not state that validity was assessed. However, the level of blinding was reported.

Effect sizes (ESs) were calculated for each study; where studies reported sufficient data for multiple outcomes, a pooled ES was calculated for each study.

The author did not state how the data were extracted for the review, or how many reviewers performed the data extraction.

The studies were classified as showing ‘no or marginal effects of prayer’ or showing ‘at least partially significant effects’ of prayer and combined in a narrative. In addition, pooled Hedge’s ESs were calculated using fixed-effect and random-effect models; individual ESs were weighted but no details were reported. Analyses were conducted with and without one study which was reported by the author to be the most controversial (reasons for the controversy were not reported).

Seventeen studies (n=3,713) were included: 14 randomised controlled trials (RCTs; n=3,661), one prospective double-blind matched study (n=16), one quasi-experimental study (n=26) and one prospective triple-blind study (n=10). The sample size ranged from 10 to 1,691; the sample size was less than 50 in 10 studies.

One of the 14 RCTs was triple-blind, twelve were double-blind and one was retroactive.

Ten studies (including 8 RCTs) reported no significant differences in outcomes between intercessory prayer and control groups.

Seven studies (including 6 RCTs) reported significant improvements in some outcomes in patients receiving intercessory prayer compared with control.

The meta-analysis showed small significant beneficial effects for intercessory prayer compared with control when using both random-effects and fixed-effect models: ES -0.171 (p=0.015) and ES -0.095 (p=0.006), respectively.

Review findings about the effects of intercessory prayer were inconclusive.

The review question was stated. Inclusion criteria were broad for the participants and study design, and not defined for the outcomes. Several relevant sources were searched, but no specific attempts to identify unpublished studies were reported and it was not clear whether any language restrictions had been applied. Limiting the validity assessment to the level of blinding means that it is not possible to adequately comment on the reliability of the results presented. The methods used to select studies and extract the data were not described, so it is not known whether any efforts were made to reduce reviewer error and bias. The narrative synthesis was appropriate in view of the diversity of the studies. The lack of results data for individual outcomes means it is not possible to confirm the findings reported in the review. Several of the included studies assessed multiple outcomes and, as the author acknowledged, this could have led to type I errors. Given the considerable clinical heterogeneity between the studies it might not have been appropriate to pool the data. The author’s conclusion that the review findings were inconclusive appears to reflect the differences between the studies, but the lack of reporting of review methods means that the conclusions should be interpreted with caution.

Practice: The author stated that until further research is conducted, intercessory prayer should generally be avoided in practice settings.

Research: The author stated that for practitioners who adhere to protocols developed by the American Psychological Association’s Division 12, there is need for further research to evaluate the effects of specific prayers offered for patients with diseases classifiable using the Diagnostic and Statistical Manual of Mental Disorders criteria.

Not stated.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.