Letter to the Editor: Comment on Schuch et al., “Exercise as a treatment for depression: A meta-analysis adjusting for publication bias”

We write to express our concern regarding the meta-analysis by Schuch et al. (2016) published in a previous issue of this journal. This meta-analysis investigates the efficacy of exercise as a treatment for major depressive disorder (MDD). Its main conclusion is that exercise is an effective treatment for MDD, and that its efficacy has been underestimated due to publication bias. Unfortunately, this last conclusion is based on a methodological error, as we detail in this letter. This meta-analysis has been very influential, receiving over 1600 citations to date, many of which recent. This includes influential policy documents, such as by the World Health Organization (2020) and the National Institute for Health and Care Excellence (2022). Hence, we think it is essential to correct the record. Furthermore, because meta-analyses are influential publications that should be beyond reproach, understanding these methodological flaws is important for all researchers.