Table 3. Methodological quality of included studies.

	Barlow et al.(2010)	Constantino & Bricker (1996)	Constantino et al. (2001)	De Groot et al. (2010)	Farberow (1992)	Kovac & Range (2000)	Wittouck et. al (2014)
Selection Bias	Weak	Weak	Weak	Weak	Weak	Moderate	Weak
Representative?	Not likely	Not likely	Not likely	Somewhat likely	Not likely	Somewhat likely	Not likely
Percentage agreement1	60–79%	80–100%	Can`t tell	Less than 60%	Can`t tell	60–79%	80–100%
Study Design	Moderate	Strong	Strong	Weak	Moderate	Strong	Strong
Study Design	Cohort (one group pre and post)	RCT	RCT	Secondary analyses of an RCT	Cohort analytic (two groups pre and post)	Controlled Clinical trial	RCT
Described as randomized?	No	Yes	Yes	Yes	No	Yes	Yes
Method of randomization described?	N.A.	Yes	Yes	Yes2	N.A.	No	Yes
Method appropriate?	N.A.	Yes	Yes	Yes	N.A.	N.A.	Yes
Confounders	N.A.	Strong	Strong	Strong	Weak	Weak	Strong
Important pre-intervention differences?		No	No	Yes	Yes	Yes	Yes
Percentage confounders controlled for?		N.A	N.A	0–100%	Less than 60%	Less than 60%	80–100%
Blinding	Weak	Weak	Weak	Weak	Weak	Strong	Weak
Outcome assessor described as blinded?	No	No	No	No	No	Yes	No
Participants blinded?	No	Can`t tell	Can`t tell	Can`t tell	Can`t tell	Yes	Can`t tell
Data Collection Method	Strong	Weak	Weak	Strong	Weak	Weak	Strong
Measures valid?	Yes	Can`t tell	Can`t tell	Yes	No	No	Yes
Measures reliable?	Yes	Yes	Yes	Yes	No	Yes	Yes
Withdrawals and Dropouts	Weak	Strong	Moderate	Strong	Weak	Moderate	Strong
Number and reasons reported per group?	No	Can`t tell	No	Yes	Can`t tell	Yes	Yes
Percentage completing study?	Less than 60%	80–100%	60–79%	80–100%	Can`t tell	Less than 60%	80–100%
Number of strong ratings	1/6	3/6	2/6	4/6	0/6	2/6	4/6
Intention-to-treat analysis	No	No	Can`t tell	Yes	Yes	No	No

¹ Refers to the % of subjects in the control and intervention group that agreed to participate in the study before they were assigned to intervention or control group.

² described in De Groot et al. (2007), RCT = randomized controlled trial