Supplementary table 1. Methodological quality of the randomized and non-randomized studies based on Downs and Black checklist (n=23) I. Checklist items from 1-10 (Reporting)
Study 1 2 3 4 5 6 7 8 9 10 Sum
Sivaramakrishnan 2017 1 1 1 1 0 1 1 0 1 0 7
Yasar 2015 1 1 1 1 0 0 1 0 1 0 6
Kuhn 2014 1 0 1 1 0 1 1 0 1 1 7
Tancredo 2013 1 0 1 1 0 1 0 0 1 0 5
Sadowsky 2013 1 1 1 1 0 1 0 0 1 1 7
Ralston 2013 1 1 1 1 0 1 1 0 1 0 7
Mazzoleni 2013 1 0 1 1 0 1 1 0 1 0 6
Carty 2013 1 1 1 1 0 0 1 0 1 1 7
Reichenfelser 2012 1 0 1 1 0 1 0 0 1 0 5
Szecsi 2009 1 0 1 1 0 1 1 0 1 1 7
Krause 2008 1 1 1 1 0 1 0 0 1 1 7
Van der Salm 2006 1 1 1 1 0 1 0 0 1 0 6
Van der Salm 2006* 1 0 1 1 0 1 0 0 1 0 5
Knikou 2005 1 0 1 1 0 1 0 0 1 0 5
Krause 2003 1 1 1 1 0 1 0 0 1 1 7
Knikou 2002 0 0 1 1 0 1 0 0 1 0 4
Mirbagheri 2002 0 0 1 1 0 1 0 0 1 0 4
Skold 2002 1 1 1 1 0 1 1 0 1 1 8
Seib 1994 1 0 1 1 0 1 1 0 1 0 6
Granat 1993 1 1 1 1 0 1 1 0 1 1 8
Douglas 1991 1 1 1 1 0 1 1 0 0 1 7
Robinson 1988 1 0 1 1 0 1 1 0 1 1 7
Franek 1988 1 1 1 1 0 1 1 0 0 1 7
II. Checklist items from 11-13 (External validity)
Study 11 12 13 Sum
Sivaramakrishnan 2017 1 1 1 3
Yasar 2015 1 1 1 3
Kuhn 2014 1 1 1 3
Tancredo 2013 1 1 1 3
Sadowsky 2013 1 1 1 3
Ralston 2013 1 1 1 3
Mazzoleni 2013 Unable to determine Unable to determine 1 1
Carty2013 1 1 1 3
Reichenfelser 2012 0 0 1 1
Szecsi 2009 Unable to determine Unable to determine 1 1
Krause2008 1 1 1 3
Van der Salm 2006 (a) 1 1 1 3
Van der Salm 2006 (b) 1 1 1 3
Knikou 2005 Unable to determine Unable to determine 1 1
Krause 2003 Unable to determine Unable to determine 1 1
Knikou 2002 Unable to determine Unable to determine 1 1
Mirbagheri 2002 Unable to determine Unable to determine 1 1
Skold 2002 Unable to determine Unable to determine 1 1
Seib 1994 Unable to determine Unable to determine 1 1
Granat 1993 Unable to determine Unable to determine 1 1
Douglas1991 Unable to determine Unable to determine Unable to determine 0
Robinson 1988 Unable to determine Unable to determine 1 1
Franek1988 Unable to determine Unable to determine 1 1
III. Checklist items from 14-26 (Internal validity)
Study 14 15 16 17 18 19 20 21 22 23 24 25 26 Sum
Bias Cofounding (selection Bias)
Sivaramakrishnan 2017 1 1 1 1 1 1 1 1 1 1 1 0 1 12
Yasar2015 0 0 1 1 1 1 1 0 1 0 0 0 1 7
Kuhn 2014 0 0 1 1 1 1 1 0 1 0 0 0 1 7
Tancredo 2013 0 0 1 0 0 1 1 0 1 0 0 0 1 5
Sadowsky 2013 0 0 1 1 1 1 1 0 1 0 0 0 1 7
Ralston 2013 0 1 1 1 1 1 1 0 1 0 1 0 1 9
Mazzoleni 2013 0 0 1 1 1 1 1 0 1 0 0 0 1 7
Carty2013 0 0 1 1 1 1 1 0 0 0 0 0 1 6
Reichenfelser 2012 0 0 1 1 1 1 1 0 0 0 0 0 1 6
Szecsi 2009 0 0 1 1 1 1 1 0 0 0 0 0 1 6
Krause2008 0 0 1 1 1 1 1 0 0 0 0 0 1 6
Van der Salm 2006 0 1 1 0 1 1 1 0 1 0 1 1 0 8
Van der Salm 2006* 0 0 1 1 1 1 1 0 1 0 0 0 1 7
Knikou 2005 0 0 1 1 1 1 1 0 1 0 0 0 1 7
Krause 2003 0 0 1 1 1 1 1 0 1 0 0 0 1 7
Knikou 2002 0 0 1 1 1 1 1 0 0 0 0 0 1 6
Mirbagheri 2002 0 0 1 1 1 1 1 0 1 0 0 0 1 7
Skold 2002 0 0 1 1 1 1 1 Unable to
determine 1 1 Unable to
determine 0 1 8
Seib 1994 0 0 1 1 1 1 1 1 1 0 0 0 1 8
Granat 1993 0 0 1 Unable to
determine
1 1 1 1 1 0 0 0 Unable to
determine
6
Douglas1991 0 0 1 0 1 1 1 1 1 Unable to
determine Unable to
determine 0 0 6
Robinson 1988 0 0 1 1 1 1 1 1 1 0 0 1 1 9
Franek1988 0 0 1 Unable to
determine 1 Unable to
determine 1 1 1 1 Unable to
determine 0 0 6
Study Report (1-10) External Validity (11-13) Internal Validity (14-26) Power (27) Sum
