Studies	Effect of the treatment	Effect of the information	Interaction	Model	Risk of bias
Hammami et al (2016) 27	Yes	Yes	Yes	Synergistic	Low
Berna et al (2017) 33	No	No	Yes	Synergistic	Low
Schenk et al (2013) 40	Yes	No	Yes	Synergistic	Low
Lund et al (2014) 31	Yes	Yes	Yes	Antagonistic	Unclear
Faasse et al (2016) 41	Yes	Yes	Yes	Antagonistic	Unclear
Hammami et al (2010) 28	Yes	Yes	Yes	Antagonistic	High
Wise et al (2009) 42	Yes	Yes	Yes	Antagonistic	High
Rose et al (2001) 44	No	Yes	Yes	Antagonistic	High
Bergmann et al (1994) 9	Yes	Yes	Yes	Antagonistic	High
Van Der Molen et al 1988) 48	Yes	Yes	Yes	Synergistic	High
Kirsch et al (1993) 38	Yes	Yes	Yes	Synergistic	High
Penick et al (1965) 39	…	No	Yes	Synergistic	High
Uhlenhuth et al (1959) 7	…	Yes	Yes	Synergistic	High
Uhlenhuth et al (1966) 46	…	Yes	Yes	Antagonistic	High
Levine et al (1984) 45	No	Yes	Yes	Antagonistic	High
Mitchell et al (1996) 30	Yes	Yes	Yes	Antagonistic	High
Kam‐Hansen et al (2014) 25	Yes	Yes	No	Additive	Low
Butcher et al (2012) 32	No	No	No	No effect	Low
Flaten et al (2004) 35	Yes	No	No	No effect	Low
Kemeny et al (2007) 43	Yes	No	No	No effect	Low
Alasken et al (2015) 10	Yes	Yes	No	Additive	Unclear
Atlas et al (2012) 37	Yes	Yes	No	Additive	Unclear
Brandwhaite et al (1981) 36	Yes	Yes	No	Additive	High
De craen et al (2001) 16	No	No	No	No effect	High
Flaten et al (1999) 34	No	Yes	No	No effect	High
Bjorkedal et al (2011) 29	No	No	No	No effect	High
Ross et al (1962) 19	No	No	No	No effect	High
Lyerly et al (1964) 49	No	No	No	No effect	High
Walach et al (2009) 26	No	No	No	No effect	High
Mathews et al (1983) 47	No	No	No	No effect	High