A recent network meta-analysis by Zhu and colleagues reported in the Shanghai Archives of Psychiatry compared two different comparators (psychological placebo and waitlist control) in trials assessing the effectiveness of cognitive behavioral therapy (CBT) for the treatment of generalized anxiety disorder (GAD). CBT was superior to both of these control conditions, but psychological placebo was superior to waitlist. However, we argue that the term 'psychological placebo' is a misnomer because the impossibility of effectively blinding participants to treatment allocation in CBT trials makes it impossible to control for placebo effects. This failure to blind participants and therapists - and the resultant high risk of bias - was the main reason Zhu and colleagues found that the overall quality of the evidence supporting the conclusion that CBT is effective for GAD is poor. This is a general problem in all psychotherapy trials, which suffer from well-documented methodological and conceptual problems that prevent adequate placebo control and undermine casual inference. We discuss these problems and suggest potential solutions. We conclude that, while it may be difficult to remove potential bias in randomized controlled trials of psychotherapy, we can improve on the status quo by integrating basic science within applied trials to adjust for these biases and, thus, improve the strength of the causal inferences.
概述: 《上海精神医学》杂志最近刊登了一篇由朱智佩及其同事撰写的网状meta 分析文章。该meta 分析荟萃比较了采用两种不同的对照组（心理安慰剂组和等候治疗对照组）评估认知行为治疗(cognitive behavioral therapy, CBT) 对广泛性焦虑障碍(generalized anxiety disorder, GAD) 疗效的研究。CBT 优于这两种对照，但心理安慰剂优于等候治疗。然而，我们认为“ 心理安慰剂” 一词不恰当，因为在CBT 研究中受试者不可能完全不知道治疗分配，所以研究不可能真正控制安慰剂效应。无法使受试者和治疗师双盲以及因此而产生的高偏倚风险正是朱智佩及其同事发现支持CBT 治疗GAD 有效的证据整体质量差的主要原因。上述问题在所有的心理治疗研究中普遍存在，方法学问题以及概念性问题限制了安慰剂对照的作用，并削弱了对因果关系的推断作用。本文讨论了这些问题并提出可能的解决方案。我们的结论是，虽然在心理治疗的随机对照研究中可能难以完全消除潜在的偏倚，但是我们可以在进行研究时整合基础科学知识，来校正这些偏倚，改进现状，从而提高因果推论的强度。.
Keywords: cognitive behavioral therapy; generalized anxiety disorder; meta-analysis; network meta-analysis; psychological placebo; psychotherapy; randomized controlled trial.