Placebo response of sham acupuncture in patients with irritable bowel syndrome: a systematic review and meta-analysis

Acupuncture has demonstrated potential benefits in managing irritable bowel syndrome (IBS). Nevertheless, some studies suggest these benefits may stem from the placebo response to acupuncture. The present study seeks to investigate the placebo response of acupuncture therapy in IBS and the factors associated with it, by means of a systematic review and meta-analysis of pre- and post-sham acupuncture intervention data. Eight databases (PubMed, Embase, Cochrane Library, Web of Science Core Collection, China National Knowledge Infrastructure (CNKI), Wanfang Database, Chinese Scientific Journals Database (VIP), and China Biology Medicine (CBM)) were searched from their inception to July 4, 2026. Randomized controlled trials (RCTs) employing sham acupuncture as a comparator for IBS were included. Response rate was employed as the primary outcome indicator, while IBS Symptom Severity Scale (IBS-SSS) scores, IBS Quality of Life Scale (IBS-QOL) scores, and abdominal pain intensity scores were used as secondary outcome measures. The effect size of placebo response was evaluated using risk difference (RD) and the pooled change quantity of before and after intervention, and 95% confidence intervals (CI). This study also examined potential factors that could influence placebo response. Twelve RCTs involving 977 IBS patients were included. In the sham acupuncture group, the combined response rate was 0.38 (95% CI: 0.30 to 0.47), the pooled change in IBS-SSS was -60.08 (95% CI: -70.62 to -49.54), the pooled change in IBS-QOL was 8.23 (95% CI: 2.17 to 14.29), and the pooled change in abdominal pain intensity scores was -1.39 (95% CI: -1.94 to -0.84). Furthermore, studies with the Rome IV diagnostic criteria, low risk of bias, or the response rate described by the U.S. Food and Drug Administration (FDA) were more likely to yield lower placebo responses. Sham acupuncture showed a certain degree of placebo response in IBS patients in terms of response rates, IBS-SSS, IBS-QOL, and abdominal pain intensity. And several factors might have a notable effect on this placebo response. PROSPERO registration number CRD420251035956.