TABLE 2.

Methodological quality of the included studies according to the Newcastle Ottawa Scale.

References	Selection	Comparability	Outcome
	(Max. score 4)	(Max. score 2)	(Max. score 3)
Bager et al. (27)	4	2	3
Cavanaugh et al. (21)	4	2	3
Cerqueira-Silva et al. (26)	4	2	3
Eythorsson et al. (6)	4	2	3
Flacco et al. (28)	4	2	3
Hall et al. (29)	4	2	3
Hammerman et al. (7)	4	2	3
Jang et al. (30)	4	2	3
Levin-Rector et al. (22)	4	2	2
Lewis et al. (31)	4	2	3
Malhotra et al. (32)	3	2	3
Medic et al. (4)	4	2	3
Murugesan et al. (33)	4	2	3
Nisha et al. (34)	4	2	3
Nordstrom et al. (8)	4	2	2
Nunes et al. (23)	3	2	2
Plumb et al. (24)	4	2	3
Spicer et al. (25)	4	2	2