References	Risk of bias (RoB) domains a						Tier b
	Exposure KEY	Outcome KEY	Confounding KEY	Inappropriate selection	Attrition	Other sources of bias/statistics
de Vogel et al. (2013)	+	+	+	+	+	+	1
Rossi et al. (2006)	+	NR	+	+	–	+	2
Johansson et al. (2008)	+	+	+	+	+	+	1
Essén et al. (2019)	+	++	‐	+	+	+	2
Hultdin et al. (2005)	+	+	+	+	+	+	1
Weinstein et al. (2006)	+	++	+	+	+	+	1
Stevens et al. (2006)	+	+	–	+	–	+	2
Roswall et al. (2013)	–	++	+	NR	++	+	2
Beilby et al. (2010)	+	+	–	NR	+	+	2
Weinstein et al. (2003)	+	++	–	NR	NR	+	2

^a Expert judgement was translated into a rating scale for each question to be answered as follows: (++): definitely low RoB; (+): probably low RoB; (NR): not reported; (−): probably high RoB; (− −): definitively high RoB.

^b The individual rating for each question was combined by an algorithm and translated to an overall tier of reliability for each individual study (RoB tier 1: low RoB; RoB tier 2: moderate RoB; RoB tier 3: high RoB).