Sex differences in the association between body mass index and recent suicide attempts in treatment-naïve young adults with major depressive disorder

Although sex differences in suicidal behavior among young patients with major depressive disorder (MDD) are well documented, whether the association between elevated body mass index (BMI) and suicide attempts (SA) varies by sex remains inconclusive. This study examined, with stratification by sex, the associations of BMI with SA in the past 3 months and related factors in young patients with MDD, and further tested for a sex × BMI interaction. A total of 520 patients with MDD aged 18–25 years were enrolled and underwent comprehensive biochemical assessments, including measurements of glycemic parameters, lipid profiles, and thyroid hormone levels. Psychiatric evaluations were conducted using standardized scales for depressive, anxiety, and psychotic symptoms. SA was defined as a suicide attempt occurring within the past 3 months. Binary logistic regression was used for sex-stratified analyses, and a sex × overweight/obesity interaction was tested in the full-sample model. Among 520 young patients with MDD, the prevalence of overweight/obesity did not differ significantly by sex ( P > 0.05). Among males, SA was more prevalent in those without overweight/obesity than in those with it (24.5% vs. 12.5%, P < 0.05), whereas no such difference was observed among females (18.7% vs. 15.0%, P > 0.05). After adjustment for SBP, DBP, TSH, and education level, overweight/obesity was independently associated with lower odds of SA in males (OR = 0.32, P = 0.005, 95% CI 0.15–0.71), but not in females. After stratification by sex and BMI, the factors associated with SA differed across subgroups: HAMD score in males with overweight/obesity (OR = 1.32, P = 0.049, 95% CI 1.002–1.73); age (OR = 1.73, P = 0.01, 95% CI 1.12–2.68), HAMA score (OR = 1.91, P = 0.002, 95% CI 1.27–2.87), and BMI (OR = 0.38, P = 0.01, 95% CI 0.19–0.77) in males without overweight/obesity; HAMA score (OR = 1.32, P = 0.02, 95% CI 1.05–1.66) and TPOAb level (OR = 2.29 per 1-SD increment, P = 0.02, 95% CI 1.13–4.62) in females with overweight/obesity; and HAMD score (OR = 1.38, P = 0.04, 95% CI 1.01–1.89) in females without overweight/obesity. However, the sex × overweight/obesity interaction was not significant ( P = 0.24), so these stratified differences should be interpreted as descriptive rather than definitive sex-specific findings. This study suggests that, among young patients with MDD, the association between elevated BMI and SA and the related factors show different patterns when stratified by sex. Larger-scale and specifically designed studies, incorporating formal interaction tests and mechanistic measures, are warranted to further validate these descriptive observations.