Table 5.

Risk of bias assessment for included observational studies.

Study Authors, Year	Bias Due to Confounding	Bias in Selection of Participants into the Study	Bias in Classification of Interventions	Bias Due to Deviations from Intended Interventions	Bias Due to Missing Data	Bias in Measurement of Outcomes	Bias in Selection of the Reported Results	Overall Risk of Bias Judgment
Kane et al., 2002	No information	No information	Low	No information	No information	Moderate	No information	No information
Nadash, 2004	Moderate	Low	Low	No information	Moderate	Moderate	No information	Moderate
Nadash, 2013	Low	Low	Low	No information	No information	Moderate	No information	Moderate
Weaver et al., 2008	Moderate	Moderate	Moderate	No information	No information	Moderate	No information	No information
Wieland et al., 2010	High	Low	Low	Low	No information	Low	Low	Low
Wieland et al., 2013	High	Low	Low	Low	No information	Low	No information	Low