〔Abstract〕 Abstract Objective To explore the characteristic of obesity in adolescents with major depressive disorder and its relationship with inflammatory cytokines . Methods One hundred and forty adolescents with major depressive disor- der were enrolled . According to the classification standard of body mass index (BMI) for adolescents in China , the patients were classified into underweight group , normal group , overweight group and obese group . The center for epidemiologic studies depression scale (CES-D) was used to evaluate symptoms of depression in patients , and ul- trasensitive multiplex electrochemiluminescence detection technology was used to measure the levels of plasma in- flammatory cytokines including interleukin(IL)-6 , IL-17A , IL-1β, IL-6 , IL-8 and tumour necrosis factor(TNF) -α. One-way ANOVA or Kruskal-Wallis H test and chi-square test were used for comparison between groups . Binary Logistic regression was used to analyze the influencing factors of obesity in adolescent patients with major depressive disorder. Results Among the 140 adolescent patients with major depressive disorder , wasting were 9. 3% ( 13/ 140) , overweight were 17. 9% (25/140) and obesity were 6. 4% (9/140) respectively . There were statistically significant differences in gender ( χ2 = 8. 301 , P < 0. 05 ) and inflammatory cytokines IL-6 ( H = 16. 217 , P < 0. 01) , IL-8 (H = 10. 926 , P < 0. 05) and TNF-α(H = 7 . 879 , P < 0. 05) among the four groups . Analysis of co- variance showed that the difference in levels of the inflammatory cytokine IL-6 (F = 4. 486 , P < 0. 01) remained statistically significant after controlling for age , gender and antidepressant use . The results of multiple comparisons showed that compared with the wasting group , the plasma IL-6 (Z = - 3 . 843 , P Bonferroni calibrate < 0. 01) were higher in the obese group;compared with the normal group , the obesity rate of males was higher than that of females ( χ2 = 8 . 812 , P Bonferroni calibrate < 0. 01) , and the level of IL-6 in the obese group (Z = - 3 . 023 , P Bonferroni calibrate < 0. 05) was higher. Binary Logistic regression analysis showed that plasma IL-6 (OR = 2. 500 , P < 0. 01) and gender (OR = 11 . 292 , P < 0. 01) were independent influencing factors for obesity in patients with adolescent depressive disor- ders . Conclusion There are gender differences in obesity rates in adolescents with depressive disorders , and obe- sity is associated with elevated levels of inflammatory cytokines .