Table 1

Methodological quality of articles (n=106)

Inclusion criteria		Design			Attrition		Attrition between groups		Exclusion after		Follow-up period		Occasion of measurement		Same pre–post measurement		Normalisation of DV measurement	Control techniques		Construct definition	Imputing missing data
Yes	No or N/A*	Pre-experimental	Quasi experimental	Experimental	Yes	No or N/A*	Yes	No or N/A*	Yes	No or N/A*	Yes	No or N/A*	One	Two or more	Yes	No or N/A*		Yes	No or N/A*		Yes	No or N/A*
99	1	7.7	33.7	58.7	48.1	51.9	28.9	62.9	22.1	77.9	32.7	67.3	70.2	29.8	70.2	29.8	100	70.2	29.8	100	19.2	80.8