BACKGROUND: Irritable bowel syndrome (IBS) is a common, chronic disorder that leads to decreased health-related quality of life and work productivity. A previous version of this review was not able to draw firm conclusions about the effectiveness of homeopathic treatment for IBS and recommended that further high quality RCTs were conducted to explore the clinical and cost effectiveness of homeopathic treatment for IBS. Two types of homeopathic treatment were evaluated in this systematic review: 1. Clinical homeopathy where a specific remedy is prescribed for a specific condition; 2. Individualised homeopathic treatment, where a homeopathic remedy based on a person's individual symptoms is prescribed after a detailed consultation.OBJECTIVES: To assess the effectiveness and safety of homeopathic treatment for IBS.SEARCH METHODS: For this update we searched MEDLINE, CENTRAL, Embase, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Allied and Complementary Medicine Database (AMED), the Cochrane IBD Group Specialised Register and trials registers from inception to 31 August 2018.SELECTION CRITERIA: Randomised controlled trials (RCTs), cohort and case-control studies that compared homeopathic treatment with placebo, other control treatments, or usual care, in adults with IBS were considered for inclusion.DATA COLLECTION AND ANALYSIS: Two authors independently assessed the risk of bias and extracted data. The primary outcome was global improvement in IBS as measured by an IBS symptom severity score. Secondary outcomes included quality of life, abdominal pain, stool frequency, stool consistency, and adverse events. The overall certainty of the evidence supporting the primary and secondary outcomes was assessed using the GRADE criteria. We used the Cochrane risk of bias tool to assess risk of bias. We calculated the mean difference (MD) and 95% confidence interval (CI) for continuous outcomes and the risk ratio (RR) and 95% CI for dichotomous outcomes.MAIN RESULTS: Four RCTs (307 participants) were included. Two studies compared clinical homeopathy (homeopathic remedy, asafoetida or asafoetida plus nux vomica) to placebo for IBS with constipation (IBS-C). One study compared individualised homeopathic treatment (consultation plus remedy) to usual care for the treatment of IBS in female patients. One study was a three armed RCT comparing individualised homeopathic treatment to supportive listening or usual care. The risk of bias in three studies (the two studies assessing clinical homeopathy and the study comparing individualised homeopathic treatment to usual care) was unclear on most criteria and high for selective reporting in one of the clinical homeopathy studies. The three armed study comparing individualised homeopathic treatment to usual care and supportive listening was at low risk of bias in four of the domains and high risk of bias in two (performance bias and detection bias).A meta-analysis of the studies assessing clinical homeopathy, (171 participants with IBS-C) was conducted. At short-term follow-up of two weeks, global improvement in symptoms was experienced by 73% (46/63) of asafoetida participants compared to 45% (30/66) of placebo participants (RR 1.61, 95% CI 1.18 to 2.18; 2 studies, very low certainty evidence). In the other clinical homeopathy study at two weeks, 68% (13/19) of those in the asafoetida plus nux vomica arm and 52% (12/23) of those in the placebo arm experienced a global improvement in symptoms (RR 1.31, 95% CI 0.80 to 2.15; very low certainty evidence). In the study comparing individualised homeopathic treatment to usual care (N = 20), the mean global improvement score (feeling unwell) at 12 weeks was 1.44 + 4.55 (n = 9) in the individualised homeopathic treatment arm compared to 1.41 + 1.97 (n=11) in the usual care arm (MD 0.03; 95% CI -3.16 to 3.22; very low certainty evidence).In the study comparing individualised homeopathic treatment to usual care, the mean IBS symptom severity score at 6 months was 210.44 + 112.4 (n = 16) in the individualised homeopathic treatment arm compared to 237.3 + 110.22 (n = 60) in the usual care arm (MD -26.86, 95% CI -88.59 to 34.87; low certainty evidence). The mean quality of life score (EQ-5D) at 6 months in homeopathy participants was 69.07 (SD 17.35) compared to 63.41 (SD 23.31) in usual care participants (MD 5.66, 95% CI -4.69 to 16.01; low certainty evidence).For In the study comparing individualised homeopathic treatment to supportive listening, the mean IBS symptom severity score at 6 months was 210.44 + 112.4 (n = 16) in the individualised homeopathic treatment arm compared to 262 + 120.72 (n = 18) in the supportive listening arm (MD -51.56, 95% CI -129.94 to 26.82; very low certainty evidence). The mean quality of life score at 6 months in homeopathy participants was 69.07 (SD 17.35) compared to 63.09 (SD 24.38) in supportive listening participants (MD 5.98, 95% CI -8.13 to 20.09; very low certainty evidence).None of the included studies reported on abdominal pain, stool frequency, stool consistency, or adverse events.AUTHORS' CONCLUSIONS: The results for the outcomes assessed in this review are uncertain. Thus no firm conclusions regarding the effectiveness and safety of homeopathy for the treatment of IBS can be drawn. Further high quality, adequately powered RCTs are required to assess the efficacy and safety of clinical and individualised homeopathy for IBS compared to placebo or usual care.