Table 3.

Bias ratings across all studies

	Sequence generation	Allocation concealment	Blinding	Incomplete outcomea	Incomplete outcomeb	Selective reporting	Other bias
Balk-Møller	+	–	–	?	–	?	–
Black	?	?	?	+	+	+	–
Clifford	–	?	?	–	–	–	–
Craighead	?	?	?	n/a	?	+	–
Dubbert	?	?	?	+	+	+	+
Franzini	–	?	–	–	n/a	?	?
Kegler	+	+	+	+	+	?	+
Maruyama	+	?	+	n/a	–	+	–
Nyer	?	+	–	–	–	?	+
Ureda	+	?	?	?	?	?	–

^aShort term data (2–6 weeks), ^bLonger term data (> 6 weeks), − High risk of bias, + Low risk of bias,? Unclear