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

•This study used firstly dose-effect meta-analysis to explore the association between acupuncture and its effects on MDD based on previously published data.•The results of this study will be useful to physicians in clinical decision-making and will clarify the session of acupuncture in treating MDD.•The restricted cubic spline was used to approximate non-linear relationship, and compared to the traditional linear regression method, it can yield a more realistic relationship between acupuncture sessions and effects.