In this paper by Metaxa and Clarke (BMJ 2024;385:e078084, doi:10.1136/bmj-2023-078084, published 1 May 2024), this study analysed data from randomised trials of psilocybin for the treatment of depression in adults. After publication, a methodological concern was raised about an error in the calculation of standardised mean differences and whether this overestimated the benefits of psilocybin. Another concern was the inclusion of data from the same study in the analysis more than once.
The authors agreed that there were errors in the extraction of data, as well as in the use and inclusion of standard deviations and standard errors across studies included in the meta-analysis; calculation of the appropriate type of standardised mean difference; and contravention of best practice by considering multiple results from the same study within the analysis.
The authors corrected individual estimates and measures of variability across all studies, and removed results from the analysis where there was inclusion of data from the same study more than once. Statistical editors at BMJ reviewed the corrected version and are satisfied with the approach. The visual abstract has also been updated.
Overall, the main messages of the study remain unaltered. The research synthesised in the review is preliminary, it does not have clinical implications and should be subject to further research.
BMJ issued an expression of concern about this article on 4 May 2024 (doi:10.1136/bmj.q1025). This correction concludes all matters raised in the notice.