The objective of this meta-analysis was to determine the longitudinal positive effect of religion or spirituality (R/S) on mental health. We summarized 48 longitudinal studies (59 independent samples) using a random effects model. Mental health was operationalized as a continuous and a dichotomous distress measure, life satisfaction, well-being, and quality of life. R/S included participation in public and private religious activities, support from church members, importance of religion, intrinsic religiousness, positive religious coping, meaningfulness, and composite measures. The meta-analysis yielded a significant, but small overall effect size of r = .08 (95% CI: 0.06 to 0.10). Of eight R/S predictors that were distinguished, only participation in public religious activities and importance of religion were significantly related to mental health (r = .08 and r = .09, respectively; 95% CI: 0.04 to 0.11 and 0.05 to 0.12, respectively). In conclusion, there is evidence for a positive effect of R/S on mental health, but this effect is small.

Spirituality may help people to maintain a high level of well-being despite adversity, but several studies that claim to support this statement have used spirituality scales and outcome measures that have overlapping content. This practice seems to be widespread: In an exploratory survey of 8 well-cited journals we found that 26 of 58 studies used a spirituality scale that contains 25% or more of well-being items to examine whether spirituality predicts well-being or distress. These spirituality questionnaires would be more appropriate for use as indicators of the domain of quality of life called spiritual well-being. We urge researchers to only use spirituality questionnaires of which less than 25% of the items refer to emotional well-being-such as the SWB Questionnaire or the Spiritual Attitude and Involvement List-when investigating the causal relationship between spirituality and emotional well-being

Measures of spirituality often contain the dimension existential well-being (EWB). However, EWB has been found to overlap with emotional and psychological well-being. Using the Spiritual Attitude and Involvement List (SAIL), we have further investigated the overlap between aspects of spirituality and of well-being among patients with cancer, by determining a) the divergent validity of the subscales of the SAIL compared with a well-being questionnaire and b) the differences in their associations to changes in pain and fatigue, and the occurrence of negative life events. Our findings suggest that a sense of trust that one is able to cope with difficulties of life belongs to the realm of well-being, instead of spirituality. Other aspects, such as a sense of meaning in life, seem more similar to spirituality than to well-being. These results can bring researchers a step further toward constructing “pure” spirituality and well-being measures, which will allow them to investigate the (causal) relationship between these constructs.