Original studies and reviews were identified by searching the PubMed, Embase and Cochrane databases up to March 2017. 
PubMed
Original studies and reviews were identified by searching the PubMed, Embase and Cochrane databases up to March 2017. 
Embase
Original studies and reviews were identified by searching the PubMed, Embase and Cochrane databases up to March 2017. 
Cochrane databases