Despite the concern of some that it is oxymoronic to explore the effects of prayers from a scientific perspective, as prayer appears to have a different philosophical basis from physiological phenomena, numerous studies on prayer have been implemented. Moher et al. (2010) recommend that studies of prayer should adopt the Consolidated Standards of Reporting Trials guidelines. Since the seminal research by Joyce and Welldon (1965), research on prayer has continued but great diversity exists in the quality of studies that have been conducted. Comparisons across studies are difficult to make because of differing methodologies and outcome measures (Olver & Dutney, 2012). For example, Harris et al. (1999) sought to replicate the work of Byrd (1998). However, comparisons were difficult to make because of differences in methodologies and measurement.

A conceptual model regarding the nature of prayer and its relationship to health has been developed by Breslin and Lewis (2008). They identify four variables that may have an impact on positive health outcomes from prayer: physiological, psychological, placebo, and social support. Physiologically, prayer may promote a relaxation response that lowers heart rate, decreases muscle tension, and slows breathing. The feelings of peace and relaxation produced may stimulate endorphins that have an impact on the autonomic nervous system’s reaction to stress. On the psychological level, prayer may create positive emotions and increase a sense of meaning, hope, empathy, and forgiveness. For some, prayer may be viewed as a placebo or a positive form of a self-fulfilling prophecy. The social support that may accompany some prayers may serve as a protective factor against illness. Knowing that others are praying for you provides a form of social support and may have a positive effect on health and well-being. Social support may also encourage the use of health behaviors. These aspects of the model may be considered the causal mechanisms of the model because effects can be more easily measured.

In contrast, the spiritual pathways identified by Breslin and Lewis (2008) in their model are variables that may influence health outcomes; however, it is difficult to prove or reject their influence because Divine intervention is not readily measureable. Some believe that prayer works subliminally or below the perception of the person. What the pray-er believes will be the result of prayer is difficult to research because of the difficulty in understanding what the pray-er believes. Likewise the belief that prayer activates energies such as chi and thus impacts health
outcomes has not been experimentally verified. Another possible spiritual mechanism is that prayer moves across time and space and the universe to have positive effects on health. This may produce a connection between the pray-er and pray-ee leading to a unity of consciousness and promoting healing. However, this is difficult to measure because one does not always know who or how many persons are praying for an individual.

Olver and Dutney (2012) attempted to incorporate the Consolidated Standards of Reporting Trials guidelines in examining the impact of intercessory prayer on improvement in spiritual well-being. A tripleblinded methodology was used with a Christian prayer group praying for the subjects in the experimental groups. Only the principal investigator communicated with those praying for the experimental group; first names, ages, marital status, occupations, and types of cancer were provided so as to enable the prayer group to personalize their prayers for the well-being of the subjects. Outcome measures included the Functional Assessment of Chronic Illness Therapy-Spiritual Well-Being (FACIT-Sp) scale (Peterman, Fitchett, Brady, Hernandez, & Cella, 2002), which is a part of a general quality of life (QOL) scale that incorporated questions on physical, functional, social/family, and emotional well-being and included 12 additional items on spiritual well-being measurement. These factors covered items on peace, meaning, and faith; the instrument has shown good internal reliability and convergent validity. Subjects in the intercessory prayer group had a small but statistically significant improvement in spiritual well-being as well as improvement in emotional well-being. The control group manifested a decrease in functional well-being during the 6-month period, whereas the experimental group showed an improvement.