There is a growing literature exploring the placebo response within specific mental disorders, but no overarching quantitative synthesis of this research has analyzed evidence across mental disorders. We carried out an umbrella review of meta-analyses of randomized controlled trials (RCTs) of biological treatments (pharmacotherapy or neurostimulation) for mental disorders. We explored whether placebo effect size differs across distinct disorders, and the correlates of increased placebo effects. Based on a pre-registered protocol, we searched Medline, PsycInfo, EMBASE, and Web of Knowledge up to 23.10.2022 for systematic reviews and/or meta-analyses reporting placebo effect sizes in psychopharmacological or neurostimulation RCTs. Twenty meta-analyses, summarising 1,691 RCTs involving 261,730 patients, were included. Placebo effect size varied, and was large in alcohol use disorder (g = 0.90, 95% CI [0.70, 1.09]), depression (g = 1.10, 95% CI [1.06, 1.15]), restless legs syndrome (g = 1.41, 95% CI [1.25, 1.56]), and generalized anxiety disorder (d = 1.85, 95% CI [1.61, 2.09]). Placebo effect size was small-to-medium in obsessive-compulsive disorder (d = 0.32, 95% CI [0.22, 0.41]), primary insomnia (g = 0.35, 95% CI [0.28, 0.42]), and schizophrenia spectrum disorders (standardized mean change = 0.33, 95% CI [0.22, 0.44]). Correlates of larger placebo response in multiple mental disorders included later publication year (opposite finding for ADHD), younger age, more trial sites, larger sample size, increased baseline severity, and larger active treatment effect size. Most (18 of 20) meta-analyses were judged ‘low’ quality as per AMSTAR-2. Placebo effect sizes varied substantially across mental disorders. Future research should explore the sources of this variation. We identified important gaps in the literature, with no eligible systematic reviews/meta-analyses of placebo response in stress-related disorders, eating disorders, behavioural addictions, or bipolar mania.

越来越多的文献探讨了特定精神障碍中安慰剂的反应，但这项研究没有全面的定量综合分析跨精神障碍的证据。我们对精神障碍生物治疗（药物治疗或神经刺激）的随机对照试验（RCT）进行了荟萃分析。我们探讨了不同疾病的安慰剂效应大小是否不同，以及安慰剂效应增加的相关性。根据预先注册的方案，我们检索了截至 2022 年 10 月 23 日的 Medline、PsycInfo、EMBASE 和 Web of Knowledge，以获取报告精神​​药理学或神经刺激随机对照试验中安慰剂效应大小的系统评价和/或荟萃分析。纳入了 20 项荟萃分析，总结了涉及 261,730 名患者的 1,691 项随机对照试验。安慰剂效应大小各不相同，在酒精使用障碍 (g = 0.90, 95% CI [0.70, 1.09])、抑郁症 (g = 1.10, 95% CI [1.06, 1.15])、不宁腿综合征 (g = 1.41) 中安慰剂效应较大，95% CI [1.25, 1.56]）和广泛性焦虑症（d = 1.85，95% CI [1.61, 2.09]）。在强迫症（d = 0.32，95% CI [0.22, 0.41]）、原发性失眠（g = 0.35，95% CI [0.28, 0.42]）和精神分裂症谱系障碍中，安慰剂效应大小为小到中等（标准化平均变化 = 0.33，95% CI [0.22，0.44]）。多种精神障碍中安慰剂反应较大的相关因素包括较晚的出版年份（与 ADHD 的研究结果相反）、年龄较小、试验地点较多、样本量较大、基线严重程度增加以及主动治疗效果较大。根据 AMSTAR-2，大多数（20 项中的 18 项）荟萃分析被判定为“低”质量。不同精神障碍的安慰剂效应大小差异很大。未来的研究应该探索这种变异的来源。 我们发现了文献中的重要空白，没有对压力相关疾病、饮食失调、行为成瘾或躁郁症中安慰剂反应进行合格的系统评价/荟萃分析。