A literature search conducted in MEDLINE, CINAHL, Embase, Web of Science, PubMed, National Health Service National Research Register, MRC Clinical Trials directory, Database of Abstracts of Reviews of Effects (DARE), Google Scholar and the Cochrane Database of Systematic Reviews.



MEDLINE
A literature search conducted in MEDLINE, CINAHL, Embase, Web of Science, PubMed, National Health Service National Research Register, MRC Clinical Trials directory, Database of Abstracts of Reviews of Effects (DARE), Google Scholar and the Cochrane Database of Systematic Reviews.



CINAHL
A literature search conducted in MEDLINE, CINAHL, Embase, Web of Science, PubMed, National Health Service National Research Register, MRC Clinical Trials directory, Database of Abstracts of Reviews of Effects (DARE), Google Scholar and the Cochrane Database of Systematic Reviews.



Embase
A literature search conducted in MEDLINE, CINAHL, Embase, Web of Science, PubMed, National Health Service National Research Register, MRC Clinical Trials directory, Database of Abstracts of Reviews of Effects (DARE), Google Scholar and the Cochrane Database of Systematic Reviews.



Web of Science
A literature search conducted in MEDLINE, CINAHL, Embase, Web of Science, PubMed, National Health Service National Research Register, MRC Clinical Trials directory, Database of Abstracts of Reviews of Effects (DARE), Google Scholar and the Cochrane Database of Systematic Reviews.



PubMed
A literature search conducted in MEDLINE, CINAHL, Embase, Web of Science, PubMed, National Health Service National Research Register, MRC Clinical Trials directory, Database of Abstracts of Reviews of Effects (DARE), Google Scholar and the Cochrane Database of Systematic Reviews.



Google Scholar
A literature search conducted in MEDLINE, CINAHL, Embase, Web of Science, PubMed, National Health Service National Research Register, MRC Clinical Trials directory, Database of Abstracts of Reviews of Effects (DARE), Google Scholar and the Cochrane Database of Systematic Reviews.



Cochrane Database of Systematic Reviews