Abstract: We identified eight randomized trials with a total of 300 adult participants for our analysis. We did not identify any trials in children. Four trials assessed thermal biofeedback. One trial assessed rectosigmoidal biofeedback. Two trials assessed heart rate variability biofeedback. Two trials assessed electrocutaneous biofeedback. Comparators were: no treatment (symptom monitoring group; three studies), attention control (pseudomeditation; two studies), relaxation control (one study), counseling (two studies), hypnotherapy (one study), standard therapy (one study), and sham biofeedback (one study). We judged all trials to have a high or unclear risk of bias. Global/Clinical improvement The clinical benefit of biofeedback plus standard therapy compared to standard therapy alone was uncertain (RR 4.20, 95% CI 1.40 to 12.58; 1 study, 20 participants; very low-certainty evidence). The same study also compared biofeedback plus standard therapy to sham biofeedback plus standard therapy. The clinical benefit in the biofeedback group was uncertain (RR 2.33, 95% CI 1.13 to 4.80; 1 study, 20 participants; very low-certainty evidence). The clinical benefit of heart rate biofeedback compared to hypnotherapy was uncertain when measured with the IBS severity scoring system (IBS-SSS) (MD -58.80, 95% CI -109.11 to -8.49; 1 study, 61 participants; low-certainty evidence). Compared to counseling, the effect of heart rate biofeedback was unclear when measured with a composite symptom reduction score (MD 7.03, 95% CI -51.07 to 65.13; 1 study, 29 participants; low-certainty evidence) and when evaluated for clinical response (50% improvement) (RR 1.09, 95% CI 0.48 to 2.45; 1 study, 29 participants; low-certainty evidence). The clinical benefit of thermal biofeedback used in a multi-component psychological intervention (MCPI) compared to no treatment was uncertain when measured with a composite clinical symptom reduction score (MD 30.34, 95% CI 8.47 to 52.21; 3 studies, 101 participants; very low-certainty evidence), and when evaluated as clinical response (50% improvement) (RR 2.12, 95% CI 1.24 to 3.62; 3 studies, 101 participants; very low-certainty evidence). Compared to attention control, the effects of thermal biofeedback within an MCPI were unclear when measured with a composite clinical symptom reduction score (MD 4.02, 95% CI -21.41 to 29.45; 2 studies, 80 participants; very low-certainty evidence) and when evaluated as clinical response (50% improvement) (RR 1.10, 95% CI 0.72 to 1.69, 2 studies, 80 participants; very low-certainty evidence). Quality of life A single trial used overall quality of life as an outcome measure, and reported that both the biofeedback and cognitive therapy groups improved after treatment. The trial did not note any between-group differences, and did not report any outcome data. Adverse events Only one of the eight trials explicitly reported adverse events. This study reported no adverse events in either the biofeedback or cognitive therapy groups (RD 0.00, 95% CI -0.12 to 0.12; 29 participants; low-certainty evidence). There is currently not enough evidence to assess whether biofeedback interventions are effective for controlling symptoms of IBS. Given the positive results reported in small trials to date, biofeedback deserves further study in people with IBS. Future research should include active control groups that use high provider-participant interaction, in an attempt to balance non-specific effects of interventions between groups, and report both commonly used outcome measures (e.g. IBS-SSS) and historical outcome measures (e.g. the composite primary symptom reduction (CPSR) score) to allow for meta-analysis with previous studies. Future studies should be explicit in their reporting of adverse events.

Plain-language summary: We searched for studies that compared biofeedback to either no treatment, sham treatment, or to other active treatments for IBS. We reviewed eight trials that included 300 total participants and assessed the effect of biofeedback on IBS. Each of these studies only included adults, and was carried out in an outpatient setting. The studies ranged from eight weeks to six months in length. The types of biofeedback devices varied, and included heart rate variability, measures of skin temperature or electrical resistance, and the tension of the muscles of the anus. None of the included trials disclosed funding sources. Our primary clinical outcomes were global clinical improvement and quality of life. Regarding overall improvement, three trials compared biofeedback to no treatment and found that biofeedback as part of a relaxation training program led to better symptom control than no treatment (very low-certainty evidence). Two of these trials also compared biofeedback to an attention control and found minimal symptom improvement, but the effects of chance could not be ruled out because the evidence was of very low-certainty. One trial found a greater symptom benefit with heart rate biofeedback compared to hypnotherapy (low-certainty evidence). Of two trials comparing biofeedback to counseling, any apparent effect was minimal and the effect of chance could not be ruled out (very low-certainty evidence). When rectosigmoidal biofeedback was compared to relaxation control, the effect favored the relaxation control. The addition of biofeedback to standard medical therapy was superior to medical therapy alone and to medical therapy plus sham biofeedback (low-certainty evidence for both findings). A single trial looked specifically at overall quality of life. Quality of life improved both for those in the biofeedback group and those in the cognitive therapy group, but there was no overall difference between groups. Only one trial explicitly reported on adverse events. It reported no adverse events in either the biofeedback group or the cognitive therapy group. We used the GRADE criteria to assess the certainty of the evidence for each of these findings. These ranged from low to very low. The evidence is current up to July 2019. We conclude that the existing data on biofeedback for IBS are limited and leave us uncertain about its value in IBS symptom management. The studies currently available all have design limitations that make the results difficult to apply to clinical settings. We do, however, recommend further study in this area, as biofeedback could represent a unique approach for a difficult to manage condition.