Zendle et al. (2023) is a study of the impact of a Chinese policy restricting heavy videogame play among minors, finding that the policy had no effect. We show that, due to flaws in design, the study could not—even in principle—causally identify the minors-targeted policy effect, which it claims to have measured: the data lacked age information, thus rendering the study incapable of answering its own research question. This warrants a formal Expression of Concern under the COPE guidelines. Context The concerns were originally shared with the authors of the target study (Zendle et al. 2023) after the study’s publication. Because the authors dismissed these issues as inconsequential, we submitted them as a Matters Arising commentary to Nature Human Behaviour, which had published the study. However, the journal rejected the commentary, for which we submitted the work to the present journal for independent evaluation.
Karhulahti et al. (Thu,) studied this question.