Department of Psychology, Occupational Psychology, University of Freiburg, Freiburg, Germany.
Department of Psychosomatic Medicine and Psychotherapy, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
Sci Rep. 2023 Mar 4;13(1):3640. doi: 10.1038/s41598-023-30362-z.
The use of open-label placebos (OLPs) has shown to be effective in clinical trials. We conducted a systematic review and meta-analysis to examine whether OLPs are effective in experimental studies with non-clinical populations. We searched five databases on April 15, 2021. We conducted separate analyses for self-reported and objective outcomes and examined whether the level of suggestiveness of the instructions influenced the efficacy of OLPs. Of the 3573 identified records, 20 studies comprising 1201 participants were included, of which 17 studies were eligible for meta-analysis. The studies investigated the effect of OLPs on well-being, pain, stress, arousal, wound healing, sadness, itchiness, test anxiety, and physiological recovery. We found a significant effect of OLPs for self-reported outcomes (k = 13; standardized mean difference (SMD) = 0.43; 95% CI = 0.28, 0.58; I = 7.2%), but not for objective outcomes (k = 8; SMD = - 0.02; 95% CI = - 0.25, 0.21; I = 43.6%). The level of suggestiveness of the instructions influenced the efficacy of OLPs for objective outcomes (p = 0.02), but not for self-reported outcomes. The risk of bias was moderate for most studies, and the overall quality of the evidence was rated low to very low. In conclusion, OLPs appear to be effective when examined in experimental studies. However, further research is needed to better understand the mechanisms underlying OLPs.
开放式安慰剂（OLP）在临床试验中已被证明是有效的。我们进行了一项系统评价和荟萃分析，以检查 OLPs 在非临床人群的实验研究中是否有效。我们于 2021 年 4 月 15 日在五个数据库中进行了检索。我们分别对自我报告和客观结果进行了分析，并检查了指示的暗示程度是否会影响 OLPs 的疗效。在 3573 条记录中，有 20 项研究纳入了 1201 名参与者，其中 17 项研究符合荟萃分析的条件。这些研究调查了 OLPs 对幸福感、疼痛、压力、唤醒、伤口愈合、悲伤、瘙痒、考试焦虑和生理恢复的影响。我们发现 OLPs 对自我报告结果有显著影响（k=13；标准化均数差（SMD）=0.43；95%置信区间（CI）=0.28, 0.58；I²=7.2%），但对客观结果没有影响（k=8；SMD=−0.02；95%CI=−0.25, 0.21；I²=43.6%）。指示的暗示程度会影响 OLPs 对客观结果的疗效（p=0.02），但不会影响自我报告结果。大多数研究的偏倚风险为中度，证据的总体质量被评为低到极低。总之，OLPs 在实验研究中似乎是有效的。然而，需要进一步的研究来更好地理解 OLPs 的作用机制。
