As described by Cochrane's publisher, Wiley, libel and slander are both forms of defamation. Further details, including responsibilities around these, are available on the publisher website: https://authorservices.wiley.com/ethics-guidelines/dual-publication-plagiarism-and-defamation.html.
"Editors should be alert to language in both submitted manuscripts and also in peer review reports or correspondence which could give rise to legal action for defamation or negligent misstatement. Such language, which can be directed at corporate entities and associations as well as individuals, should not appear within published articles and should be removed from any peer review report or correspondence that is passed on to the author." Source: https://authorservices.wiley.com/ethics-guidelines/editorial-standards-and-processes.html (accessed )
If you need to raise a concern, contact Karla Soares-Weiser (firstname.lastname@example.org), Editor in Chief.