Table 2.

Quality assessment of included studies.

Reference	EPHPP Section ratings (strong/moderate/weak)						Global rating	Jadad score(0–5)
	Selection bias	Study design	Confounders	Blinding	Data collection	Withdrawals
Randomized controlled trials (RCTs)
Kemmerich et al. 2006	moderate	strong	strong	strong	weak	strong	strong	5
Unkauf and Friedrich 2000	weak	strong	moderate	weak	weak	strong	weak	2
Controlled trials (CCTs)
Bolbot et al. 2004	moderate	moderate	weak	weak	moderate	strong	weak	n.a.
Observational studies (OSs)
Büechi and Kähler 2003	weak	moderate	weak	weak	weak	weak	weak
Büechi et al. 2005	weak	moderate	weak	weak	weak	strong	weak
Fazio et al. 2009	moderate	moderate	weak	weak	weak	strong	weak
Hecker 1999	weak	moderate	weak	weak	weak	weak	weak	n.a.
Leskow 1985	weak	moderate	moderate	weak	weak	weak	weak
Marzian 2007	moderate	moderate	weak	weak	weak	weak	weak
Santoro Júnior 2005	moderate	moderate	moderate	weak	weak	strong	weak

n.a. = not applicable.