Table 2.

Methodological quality of included RCT

Study	Validity criteria met*	Methodological quality†
Hardy et al28	a, b, c, g, h, i, j	High
Pop-Eleches et al29	a, c, g, h, i, j, k	High
Hou et al30	a, b, c, f, g, h, i, j, k	High
Strandbygaard et al31	a, c, g, h, i, j	High
Simoni et al39	a, b, c, g, h, i, j, k	High
Charles et al34	a, b, c, g, h, i, j	High
Andrade et al36	c, g, h, i, j, k	High
Christensen et al32	c, g, h, j	Low
Ho et al33	g, h, j	Low
Santschi et al35	a, g, h, i	Low
Da Costa et al37	c, g, h, j	Low
Safren et al40	c, g, h, j, k	Low
Laster et al38	g, h, i, j	Low

^*Selection bias: criteria a, b, c; performance bias: criteria d, e, g and h; attrition bias: criteria i and k; detection bias: criteria f and j.

^†High quality: six or more criteria met; low quality: five or fewer criteria met.

RCT, randomised controlled trial.