Included trials (year of publication)	Domains
	1	2	3	4	5	Overall risk of bias
Kam‐Hansen et al (2014) 25	Low	Low	Low	Low	Low	Low
Walach et al (2009) 26	Low	Low	Low	Low	High	High
Hammami et al (2016) 27	Low	Low	Low	Low	Low	Low
De Craen et al (2001) 16	Some concerns	High	Low	Some concerns	High	High
Hammami et al (2010) 28	Low	Low	Low	Low	High	High
Bjorkedal et al (2011) 29	Low	Low	Low	Low	High	High
Mitchell et al (1996) 30	Low	High	Low	Low	Some concerns	High
Aslasken et al (2015) 10	Some concerns	Some concerns	Low	Low	Low	Some concerns
Lund et al (2014) 31	Low	Low	Low	Low	Some concerns	Some concerns
Butcher et al (2012) 32	Low	Low	Low	Low	Low	Low
Berna et al (2017) 33	Low	Low	Low	Low	Low	Low
Flaten et al (1999) 34	Low	Low	Low	Low	High	High
Flaten et al (2004) 35	Low	Low	Low	Low	Low	Low
Brandwhaite et al (1981) 36	Low	Low	Low	Low	Some concerns	Low
Atlas et al (2012) 37	Some concerns	Some concerns	Low	Some concerns	Some concerns	Some concerns
Kirsch et al (1993) 38	Low	Some concerns	Low	Low	High	High
Penick et al (1965) 39	High	High	Low	High	Low	High
Schenk et al (2014) 40	Low	Low	Low	Low	Low	Low
Faasse et al (2016) 41	Low	Some concerns	Low	Some concerns	Some concerns	Some concerns
Wise et al (2009) 42	Low	Low	Low	Low	High	High
Kemeny et al (2007) 43	Low	Low	Low	Low	Low	Low
Rose et al (2001) 44	Low	Low	Some concerns	Some concerns	High	High
Ross et al (1962) 19	Some concerns	Some concerns	Some concerns	Some concerns	Some concerns	High
Levine et al (1984) 45	Low	Some concerns	Some concerns	Some concerns	Low	High
Uhlenhuth et al (1959) 7	Low	Low	Some concerns	Some concerns	Low	High
Uhlenhuth et al (1966) 46	Low	Some concerns	Some concerns	Low	High	High
Mathews et al (1983) 47	Some concerns	High	Some concerns	Some concerns	Low	High
Van Der Molen et al (1988) 48	Some concerns	Some concerns	Low	Some concerns	High	High
Lyerly et al (1964) 49	Some concerns	Some concerns	Low	Some concerns	High	High
Bergmann et al (1994) 9	Low	Low	Some concerns	Low	Low	Some concerns