Thrane, S., & Cohen, S.M. (2014). Effect of reiki therapy on pain and anxiety in adults: An in-depth literature review of randomized trials with effect size calculations. Pain Management Nursing, 15, 897–908. 

STUDY PURPOSE: To summarize evidence and quantify the effects of reiki on pain and anxiety

• FINAL NUMBER STUDIES INCLUDED = 7
• TOTAL PATIENTS INCLUDED IN REVIEW = 328
• SAMPLE RANGE ACROSS STUDIES: 16–60 patients
• KEY SAMPLE CHARACTERISTICS: 48% women; mean age 63 years; three studies were in patients with cancer; two studies tested the intervention in a surgical setting; two studies used reiki in community-dwelling adults

The effects sized for within-group differences ranged from d = 0.24 for decreased anxiety in women undergoing breast biopsy to d = 2.08 for decreased pain in community-dwelling adults. For reiki versus a rest intervention in patients with cancer, the effect for a decrease in pain was d = 0.032, and the effect in community-dwelling adults was d = 0.45. A detailed discussion of individual studies showed some mixed findings, particularly for one study in which reiki was compared to both sham reiki and usual-care groups. The median number of study participants was 24. It was noted that it took more than a year to recruit a small number of subjects in some trials. The timing, number of sessions, and specific applications of reiki varied.

Data were insufficient to draw any generalizations regarding the effects of reiki on anxiety or pain. The magnitude of the effect sizes calculated suggests Reiki may be helpful, but more rigorous trials with larger samples are needed to fully evaluate its efficacy.

• Limited number of studies with only three in patients with cancer
• Sample sizes were small
• No quality evaluation of studies was include
• Timing and length of the intervention varied substantially, and most were for very short durations with few reiki sessions

This review did not demonstrate clear efficacy of reiki for pain or anxiety. However, the effect sizes shown here suggest that additional, wel- designed research is warranted. The authors made a note of the difficulty in recruiting patients to these trials and high attrition rates, particularly in the control groups. They suggested that the of a crossover design would be helpful to address these problems. The timing and length of treatment needs to be considered based on the desired effects and context of the patient situation. As much as possible, the standardization of the reiki intervention and the use of a sham control would be helpful to evaluate potential placebo effects.