Abstract: Seventeen RCTs (1806 participants) were included. Five RCTs compared acupuncture versus sham acupuncture. The risk of bias in these studies was low. We found no evidence of an improvement with acupuncture relative to sham (placebo) acupuncture for symptom severity (SMD -0.11, 95% CI -0.35 to 0.13; 4 RCTs; 281 patients) or quality of life (SMD = -0.03, 95% CI -0.27 to 0.22; 3 RCTs; 253 patients). Sensitivity analyses based on study quality did not change the results. A GRADE analysis indicated that the overall quality of the evidence for the primary outcomes in the sham controlled trials was moderate due to sparse data. The risk of bias in the four Chinese language comparative effectiveness trials that compared acupuncture with drug treatment was high due to lack of blinding. The risk of bias in the other studies that did not use a sham control was high due to lack of blinding or inadequate methods used for randomization and allocation concealment or both. Acupuncture was significantly more effective than pharmacological therapy and no specific treatment. Eighty-four per cent of patients in the acupuncture group had improvement in symptom severity compared to 63% of patients in the pharmacological treatment group (RR 1.28, 95% CI 1.12 to 1.45; 5 studies, 449 patients). A GRADE analysis indicated that the overall quality of the evidence for this outcome was low due to a high risk of bias (no blinding) and sparse data. Sixty-three per cent of patients in the acupuncture group had improvement in symptom severity compared to 34% of patients in the no specific therapy group (RR 2.11, 95% CI 1.18 to 3.79; 2 studies, 181 patients). There was no statistically significant difference between acupuncture and Bifidobacterium (RR 1.07, 95% CI 0.90 to 1.27; 2 studies; 181 patients) or between acupuncture and psychotherapy (RR 1.05, 95% CI 0.87 to 1.26; 1 study; 100 patients). Acupuncture as an adjuvant to another Chinese medicine treatment was significantly better than the other treatment alone. Ninety-three per cent of patients in the adjuvant acupuncture group improved compared to 79% of patients who received Chinese medicine alone (RR 1.17, 95% CI 1.02 to 1.33; 4 studies; 466 patients). There was one adverse event (i.e. acupuncture syncope) associated with acupuncture in the 9 trials that reported this outcome, although relatively small sample sizes limit the usefulness of these safety data. Sham-controlled RCTs have found no benefits of acupuncture relative to a credible sham acupuncture control for IBS symptom severity or IBS-related quality of life. In comparative effectiveness Chinese trials, patients reported greater benefits from acupuncture than from two antispasmodic drugs (pinaverium bromide and trimebutine maleate), both of which have been shown to provide a modest benefit for IBS. Future trials may help clarify whether or not these reportedly greater benefits of acupuncture relative to pharmacological therapies are due entirely to patients’ preferences for acupuncture or greater expectations of improvement on acupuncture relative to drug therapy.

Plain-language summary: This review included 17 randomized controlled trials (RCTs) including a total of 1806 participants. Five RCTs (411 participants) compared acupuncture to sham acupuncture for the treatment of IBS. Sham acupuncture is a procedure in which the patient believes he or she is receiving true acupuncture. However, in sham acupuncture the needles either do not penetrate the skin or are not placed at the correct places on the body, or both. Sham acupuncture is intended to be a placebo for true acupuncture. The sham-controlled studies were well designed and of high methodological quality. These studies tested the effects of acupuncture on IBS symptom severity or health-related quality of life. None of these RCTs found acupuncture to be better than sham acupuncture for either of these two outcomes, and pooling the results of these RCTs also did not show acupuncture to be better than sham acupuncture. Evidence from four Chinese language comparative effectiveness trials showed acupuncture to be superior to two antispasmodic drugs (pinaverium bromide and trimebutine maleate), both of which provide a modest benefit for the treatment of IBS, although neither is approved for treatment of IBS in the United States. It is unclear whether or not the greater benefits of acupuncture reported by patients in these unblinded studies are due entirely to patients’ greater expectations of improvement from acupuncture than drugs or preference for acupuncture over drug therapy. There was one side effect (i.e. fainting in one patient) associated with acupuncture in the nine trials that reported side effects, although relatively small sample sizes limit the usefulness of this safety data.