Table 1.

Rating of methodological quality (risk of bias) of the included studies, in alphabetical order.

First author, year	Selection bias	Study design	Detection bias	Attrition bias	Statistical methods	Overall quality
Adachi et al. (45)	M	H	H	H	H	H
Albrecht et al. (37)	L	M	H	L	H	L
Cimino et al. (38)	L	H	H	L	H	L
Fischer et al. (36) (KLIK)	M	M	H	L	M	M
Fischer et al. (36) (NTR)	L	M	H	L	M	L
Gordon-Hacker et al. (54)	L	H	H	M	H	M
Hafstad et al. (39)	H	M	H	L	H	M
Hagihara et al. (46)	M	H	H	L	H	M
Lehmann et al. (34)	L	H	H	L	H	L
Lehmann et al. (35)	L	H	H	L	H	L
Lengua et al. (50)	L	H	H	M	H	M
Martinsone et al. (40)	L	H	H	M	H	M
Nikolaidis et al. (53)	M	H	L	L	H	L
Poulain et al. (41)	L	H	H	M	H	M
Ravens-Sieberer et al. (5)	M	H	H	M	H	H
Raymond et al. (51)	L	H	H	M	H	M
Theuring et al. (42)	M	H	H	H	H	H
van der Laan et al. (43)	M	H	H	L	H	M
Weissman et al. (52)	L	H	H	H	H	M
Wenter et al. (44)	L	M	H	L	H	L
Westrupp et al. (56)	H	H	H	M	M	M
Xie et al. (47)	M	H	H	H	M	H
Zhang et al. (48)	L	H	H	H	M	M
Zhou et al. (49)	M	M	H	L	M	M
Zuccolo et al. (55)	M	H	H	L	M	M

L, Low; M, Moderate; and H, High quality rating.