Context

Acupuncture is controversial. Even if one assumes its overall effectiveness, common explanations for its causal impact are biologically implausible. Hence acupuncture is often dismissed as ‘no more than a placebo’, and this allegation is difficult to disprove as placebo-controlled trials are problematic. ‘Placebo’ needles stimulate sensory nerves and are possibly a less active treatment, ‘sham’ rather than ‘placebo’.1 Small differences between treatments require large sample sizes, as achieved by meta-analysis. Previous meta-analyses concentrated on finding all trials, but poor quality limited the conclusions.