Table 3. Quality assessment by the Newcastle-Ottawa scale.

References	Selection	Comparability	Exposure	Overall grade
Gibson-Smith et al. [13]	****	**	***	GOOD
Gregório et al. [14]	***	**	***	GOOD
Jacka et al. [15]	****	*	***	GOOD
Vafaei et al. [18]	****	*	***	GOOD
Weng et al. [17]	****	*	***	GOOD