The dose-effect association between acupuncture sessions and its effects on major depressive disorder: A meta-regression of randomized controlled trials

Background: The benefits of acupuncture on Major depressive disorder (MDD) have been well established in previous studies. However, uncertainty exists regarding the dose-effect relationship between acupuncture and MDD. This study aims to explore the association between acupuncture and its effects on MDD based on previously published data.Methods: Nine databases were searched from inception until 10th September 2021. Randomized controlled trials that compared acupuncture with sham acupuncture, or anti-depressants, were included. The data extraction, and assessing the data quality and risk of bias completed by two researcher, respectively. A non-linear metaregression approach with restricted cubic spline was used to investigate the dose-effect relationship between acupuncture sessions and their effects on the Hamilton rating scale for depression (HAMD) score.Results: Of the 20,835 citations screened, 62 studies (2269 patients of MDD) were included. The dose-effect metaanalysis suggested that acupuncture session was associated with a decline in HAMD scores. Overall, an increase in the number of acupuncture sessions received was associated with symptom improvement in MDD patients. After 8 acupuncture sessions, the HAMD score decreased from 17.68 (95% CI: -11.81, -4.80) to 8.30 (95% CI: 14.23-21.13). After 24 acupuncture sessions, a decrease in HAMD scores was observed in 51% of cases (95% CI: 48% to 54%). After 36 acupuncture sessions, the effect of improvement in HAMD scores peaked at 66% of cases (95% CI: 59% to 72%).Conclusions: A dose-effect relationship was found between the number of acupuncture sessions and HAMD scores. 36 acupuncture sessions were associated with optimal clinical response. Systematic review registration: PROSPERO CRD42021290143.