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Risk of bias summary: review authors' judgements about each risk of bias item for each included study. Note: for trials including both a comparison with sham and a no‐acupuncture control/prophylactic drugs (Diener 2006, Facco 2008, Linde K 2005) blinding was assessed for the comparisons with sham. For the comparisons with no acupuncture/prophylactic drugs the risk of bias is high (no blinding).
