Acupuncture has been used for chronic constipation, but evidence for its effectiveness remains scarce.

To determine the efficacy of electroacupuncture (EA) for chronic severe functional constipation (CSFC).

Randomized, parallel, sham-controlled trial. (ClinicalTrials.gov: NCT01726504)

15 hospitals in China.

Patients with CSFC and no serious underlying pathologic cause for constipation.

28 sessions of EA at traditional acupoints or sham EA (SA) at nonacupoints over 8 weeks.

The primary outcome was the change from baseline in mean weekly complete spontaneous bowel movements (CSBMs) during weeks 1 to 8. Participants were followed until week 20.

1075 patients (536 and 539 in the EA and SA groups, respectively) were enrolled. The increase from baseline in mean weekly CSBMs during weeks 1 to 8 was 1.76 (95% CI, 1.61 to 1.89) in the EA group and 0.87 (CI, 0.73 to 0.97) in the SA group (between-group difference, 0.90 [CI, 0.74 to 1.10]; P  < 0.001). The change from baseline in mean weekly CSBMs during weeks 9 to 20 was 1.96 (CI, 1.78 to 2.11) in the EA group and 0.89 (CI, 0.69 to 0.95) in the SA group (between-group difference, 1.09 [CI, 0.94 to 1.31]; P < 0.001). The proportion of patients having 3 or more mean weekly CSBMs in the EA group was 31.3% and 37.7% over the treatment and follow-up periods, respectively, compared with 12.1% and 14.1% in the SA group (P < 0.001). Acupuncture-related adverse events during treatment were infrequent in both groups, and all were mild or transient.

Longer-term follow-up was not assessed. Acupuncturists could not be blinded.

Eight weeks of EA increases CSBMs and is safe for the treatment of CSFC. Additional study is warranted to evaluate a longer-term treatment and follow-up.

Ministry of Science and Technology of the People's Republic of China through the Twelfth Five-Year National Science and Technology Pillar Program.