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Background: Choice has been found to facilitate placebo effects for single-session treatments where standard placebo treatment without choice failed to elicit a placebo effect. However, it is unknown whether choice can enhance the placebo effect for treatments occurring over a period of days and where placebo effects are readily established without choice.Purpose: We tested whether single or daily choice between two (placebo) treatments enhanced the placebo effect for sleep difficulty relative to no choice and no treatment over a 1 week period.Methods: One-hundred and seventeen volunteers self-identifying with sleep difficulty were recruited under the guise of a hypnotic trial and randomized to one of the four groups. Self-reported outcomes included insomnia severity, fatigue, total sleep time (TST), sleep onset latency (SOL), perceived sleep quality (PSQ), and treatment satisfaction. Objective TST and SOL were assessed in a subsample via actigraphy.Results: Overall, placebo treatment significantly improved insomnia severity, fatigue, and PSQ, confirming a placebo effect on these outcomes. However, both traditional and Bayesian analysis indicated no benefit of choice on the placebo effect on any sleep outcome. Mediation analysis of the overall placebo effect indicated that expectancy completely mediated the placebo effects for insomnia severity and PSQ and partially mediated the placebo effect for fatigue.Conclusion: These findings suggest that choice does not enhance the placebo effect over longer treatment periods (up to 7 days) when placebo effects are readily established without choice. As such, any benefit of choice on placebo effects may be confined to quite specific circumstances.Clinical Trials Registration: ACTRN12618001199202. [ABSTRACT FROM AUTHOR]

This systematic review and meta-analysis aimed to determine the size of the placebo effect for insomnia symptoms when comparing placebo treatment with no treatment. PsycINFO, MEDLINE, and CINAHL databases were systematically searched for studies allocating participants with insomnia symptoms (diagnosed or self-reported) to receive a placebo that they were led to believe was an active treatment or to a no treatment control group. Thirteen independent studies (n = 566) met inclusion criteria. Meta-analysis indicated a reliable placebo effect whereby placebo treatment led to improved perceived sleep onset latency (SOL; Hedges g = 0.272), total sleep time (TST; Hedges g = 0.322), and global sleep quality (GSQ; Hedges' g = 0.581), when compared with no treatment. There was no effect on objective assessment of SOL, however only a few studies reported this outcome and there were insufficient sample sizes to meta-analyse other objective outcomes. Moderator analysis indicated that the placebo effect for perceived insomnia symptoms was quite consistent across different variables. The present findings provide strong evidence for placebo effects for perceived insomnia symptoms, but not on the only objective measurement with sufficient sample size to meta-analyse, namely objective SOL. This has important implications for the treatment of insomnia symptoms and the design and interpretation of clinical trials for insomnia symptoms. [ABSTRACT FROM AUTHOR]