The response of sham acupuncture in patients with primary insomnia: A systematic review and meta-analysis

Background Sham acupuncture may be associated with sham acupuncture responses in primary insomnia (PI), complicating the interpretation of acupuncture efficacy. Objective To quantify the observed sham acupuncture response intervention in patients with PI and explore potential influencing factors. Methods Eight databases were searched from inception to 1 July 2025 for randomized controlled trials (RCTs). Risk of bias was assessed using RoB 2.0 and certainty of evidence using GRADE. Outcomes were summarized using standardized mean differences (SMDs) with 95% confidence intervals (CIs) to estimate the magnitude of changes observed after sham acupuncture intervention. Results Forty-eight RCTs (n = 1741) were included. Compared with baseline, sham acupuncture groups showed improvements in subjective sleep quality (SMD = −0.71, 95% CI −0.92 to −0.51), as well as depressive (SMD = −0.46, 95% CI −0.72 to −0.20) and anxiety symptoms (SMD = −0.67, 95% CI −1.08 to −0.26). Subgroup analyses indicated that effects varied by sample size and sham type. Most objective sleep parameters showed no significant changes, although objective sleep efficiency (SE) indicated a modest but statistically significant improvement. Conclusions Sham acupuncture was associated with improvements in subjective and emotional outcomes in patients with primary insomnia, whereas most objective sleep measures showed little or no change, except for a modest but statistically significant improvement in objective SE. These findings suggest that the observed sham acupuncture responses may involve non-specific contextual factors rather than representing the effects of a completely inert control intervention.