The purpose of this study was to evaluate the effectiveness of spiritual intervention studies by examining biological, psychological, and spiritual outcomes.

From electronic databases 2522 studies were retrieved, of which 21 studies met the inclusion criteria. These studies had 1411 participants. Two authors independently extracted data from the selected studies and assessed the methodological quality. The data were analyzed using the RevMan 5.1 program of the Cochrane library.

Overall effect size of spiritual intervention on spiritual and psychological (depression and anxiety) outcomes were moderate (d=-0.65 to d=-0.76, p<.001). The effects on biological outcomes (pain and functional status) ranged from -0.51 to -0.39, respectively. No publication bias was detected as evaluated by a funnel plot. Spiritual intervention had a moderate effect on psychological and spiritual outcomes and a smaller effect on biological outcomes.

The results of this study suggest that spiritual intervention can relieve depression and anxiety. Further randomized controlled trials studies are needed to evaluate the effects of spiritual intervention on biological outcomes.