An investigation conducted on behalf of the journal by Elsevier's Research Integrity & Publishing Ethics team found a significant increase of citations to papers published by the author, Amirhossein Sahebkar, between the original submission and the revised version of this article. In summary, 6 papers by the author were cited in the original version of the article. This increased to 28 papers in the revised version of the article. Although the references are deemed to be relevant, the editors determined that an Expression of Concern is warranted to alert readers.
A Sun, study studied this question.