Reviews of empirical work on the efficacy of noncontact healing have found that adopting various practices that incorporate an intention to heal can have some positive effect upon the recipient’s wellbeing. However, such reviews focus on ‘whole’ human participants who might be susceptible to expectancy effects or benefit from the healing intentions of friends, family or their own religious groups. We proposed to address this by reviewing healing studies that involved biological systems other than ‘whole’ humans (e.g., studies of plants or cell cultures) that were less susceptible to placebo-like effects. Secondly, doubts have been cast concerning the legitimacy of some of the work included in previous reviews so we planned to conduct an updated review that excluded that work.
Only studies in English were eligible for inclusion. All studies must have examined the effects upon a biological system of the explicit intention to improve the wellbeing of that target; 49 non-whole human studies from 34 papers and 57 whole human studies across 56 papers were included.
The combined weighted effect size for non-whole human studies yielded a highly significant r of .258, but outcomes were heterogeneous and correlated with blind ratings of study quality; 22 studies that met minimum quality thresholds gave a reduced but still significant weighted r of .115. Whole human studies yielded a small but significant effect size of r = .203. Outcomes were again heterogeneous, and correlated with methodological quality ratings; 27 studies that met threshold quality levels gave an increased r = .224.
Results suggest that subjects in the active condition exhibit a significant improvement in wellbeing relative to control subjects under circumstances that do not seem to be susceptible to placebo and expectancy effects. Findings with the whole human database suggests that the effect is not dependent upon the previous inclusion of suspect studies and is robust enough to accommodate some high profile failures to replicate. Both databases show problems with heterogeneity and with study quality and recommendations are made for necessary standards for future replication attempts.
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