Article History
First Online: 22 August 2018
Compliance with Ethical Standards
:
: The authors declare that they have no conflicts of interest. JAD acknowledges that he is an author of several meta-analyses included in this review, but he was not involved in extracting any data from those meta-analyses for the purposes of this review.
: This article does not contain any studies with human participants performed by any of the authors.
: For this type of study, formal consent is not required.