A post-publication investigation conducted by Elsevier's Research Integrity & Publishing Ethics team on behalf of the journal could not confirm whether or not ethical approval was given and whether or not the participants provided informed consent for the research presented in this publication in line with the journal's policy. As it cannot be established whether the article complies with the journal's policies on ethical approval and consent, the Editors are issuing this Expression of Concern to alert readers.
A Sun, study studied this question.