Nonspecific mechanisms that enhance well-being in health-promoting behaviors.

Abstract

We tested whether the nonspecific or placebo enhancement of well-being brought about by a health-promoting behavior was due to expectancy having an unmediated effect on outcome (response expectancy theory) or because expectancy was mediated through the behavioral and affective consequences of positively valued goal satisfaction (motivational concordance theory). Fifty-seven participants completed a breathing exercise (a simplified Buteyko technique) purporting to enhance well-being over a period of 4 days. Participants were randomized to receive either easy or difficult task instructions. Expectancy was measured at baseline and perceived effort (as an indicator of motivation) and adherence were measured at follow-up. Well-being was measured by perceived change in well-being at follow-up and by change in the Positive and Negative Affect Scale between baseline and follow-up. Expectancy (r = .42), adherence (r = .57), and effort (r = .90) correlated with perceived benefit. Multiple regression and mediation analysis showed that effort predicted (p < .01) well-being independently of expectancy for all 3 measures of well-being, and that where expectancy predicted outcome, its effect was mediated by effort. Adherence failed to predict additional variance to outcome compared with effort and expectancy. These results are consistent with the hypothesis that placebo effects in therapeutic contexts are mediated via the affective consequences of performing a motivated ritual.