“…Ten studies (47%) were judged to be at moderate risk of bias [2–5, 21, 26, 29, 30, 32, 35]. Another 10 studies (47%) were at serious risk of bias [19, 20, 22–24, 27, 28, 31, 33, 34]. One study, which was a conference abstract, was considered to have a critical risk of bias [25].…”