Table 2. Risk of bias of included studies.

Included study	Random sequence generation	Allocation concealment	Blinding of patients	Blinding of therapists	Incomplete outcome data	Selective reporting	Other bias
Ball 2013	Low	Unclear	Low	Unclear	Low	Low	Unclear
Chen 2013	Unclear	Unclear	Unclear	High	Low	Low	Unclear
Kane 2001	Unclear	Unclear	Unclear	Unclear	Low	Low	Unclear
Tsai 2006	Unclear	Unclear	Unclear	Unclear	Low	Low	Unclear
Yucel 2009	Unclear	Unclear	Unclear	Unclear	Low	Low	Unclear