Abstract
Controversial evidence exists on the relationship between body mass index (BMI) and suicide attempts (SA) in patients with major depressive disorder (MDD). This cross-sectional study aimed to explore the association between BMI and SA in first-episode drug-naïve (FEDN) MDD patients in China. The study was conducted from 2016 to 2018 in Taiyuan, China. Univariate and multivariate logistic regression analyzed the BMI-SA association, with subgroup analysis for gender. Threshold effects were examined using two-piecewise regression. In males, BMI was significantly associated with SA (OR = 0.84, 95% CI 0.74-0.94, P = 0.003) after full adjustment, but not in females (OR = 0.97, 95% CI 0.89-1.06, P = 0.541). The interaction with gender was significant (P for interaction < 0.05). Smoothing plots revealed an L-shaped BMI-SA relationship in both genders, with BMI inflection points at 27.3 kg/m(2) in males and 21.4 kg/m(2) in females. Below the inflection points, BMI is negatively associated with SA in males (OR = 0.75, 95% CI 0.66-0.86, P < 0.001) and females (OR = 0.48, 95% CI 0.32-0.72, P < 0.001). Above the inflection points, no association existed for both genders (all P > 0.05). Results showed an L-shaped nonlinear BMI-SA relationship in FEDN MDD patients but differing BMI inflection points between genders, thus contributing to effective prevention programs for suicide.