Abstract：
Some recent research and commentary have suggested that most or all the effects reported by people who microdose psychedelics may be explained by expectations or placebo effects. In this rapid review, we aimed to evaluate the strength of evidence for a placebo explanation of the reported effects of microdosing. We conducted a PubMed search for all studies investigating psychedelic microdosing with controlled doses and a placebo comparator. We identified 19 placebo-controlled microdosing studies and summarised all positive and null findings across this literature. Risk of bias was assessed using the Cochrane risk-of-bias tool for randomised trials. The reviewed papers indicated that microdosing with LSD and psilocybin leads to changes in neurobiology, physiology, subjective experience, affect, and cognition relative to placebo. We evaluate methodological gaps and challenges in microdosing research and suggest eight reasons why current claims that microdosing is predominately a placebo are premature and possibly wrong: (1) there have been only a small number of controlled studies; (2) studies have had small sample sizes; (3) there is evidence of dose-dependent effects; (4) studies have only investigated the effects of a small number of doses; (5) the doses investigated may have been too small; (6) studies have looked only at non-clinical populations; (7) studies so far have been susceptible to selection bias; and (8) the measured impact of expectancy is small. Considering the available evidence, we conclude that it is not yet possible to determine whether microdosing is a placebo.
摘要：
最近的一些研究和评论表明，微剂量迷幻药的人报告的大多数或所有影响可能由预期或安慰剂效应来解释。在这次快速审查中，我们的目的是评估安慰剂对微量给药效应的解释的证据强度.我们进行了PubMed搜索所有研究迷幻微剂量控制剂量和安慰剂比较。我们确定了19项安慰剂对照的微量给药研究，并总结了这些文献中的所有阳性和无效发现。使用Cochrane偏倚风险工具对随机试验进行偏倚风险评估。综述的论文表明，LSD和psilocybin的微量给药导致神经生物学的变化，生理学,主观体验,影响，和相对于安慰剂的认知。我们评估了微剂量研究的方法学差距和挑战，并提出了八个原因，为什么目前声称微剂量主要是安慰剂是过早的，并且可能是错误的：（1）只有少量的对照研究；（2）研究样本量较小；（3）有剂量依赖性效应的证据；（4）研究仅调查了少量剂量的影响；（5）研究的剂量可能是迄今为止对临床研究的影响太小（6）考虑到现有的证据,我们得出的结论是,尚无法确定微量给药是否是安慰剂.
