Gender Determines the Pattern of Correlation between Body Mass Index and Major Depressive Disorder among Children and Adolescents: Results from Iranian Children and Adolescents' Psychiatric Disorders Study.

Background: We aimed to determine the correlation of BMI with depression and to determine the role of gender in this association, in a large study sample. Methods: We used the data of participants in the Iranian Children and Adolescents' Psychiatric Disorders (IRCAP) Study, conducted in 2017. This study was a national community-based, cross-sectional study in which the urban and rural areas of all provinces of Iran were covered. Overall 30,532 children and adolescents, ages 6-18, were randomly selected with the stratified cluster sampling method. Results: Of a total of 30,532 participants, 25,321, whose BMI had been measured and who had been interviewed with Kiddie Schedule for Affective Disorders and Schizophrenia (K-SADS), entered the study (12,455 boys and 12,866 girls). We categorized the participants according to the national cutoff points for BMI classification. After controlling for age, father's and mother's job and education, and place of residence, the odds ratio (OR) of depression in underweight, healthy weight, and overweight boys compared with obese boys was 2.19 [95% confidence interval (95% CI): 1.00-4.81], 1.06 (95% CI: 0.73-1.55), and 0.80 (95% CI: 0.49-1.32), respectively. In the girls' subgroup, after controlling for the aforementioned covariates, the OR of depression in healthy weight, overweight, and obese participants compared with underweight subjects was 1.29 (95% CI: 0.52-3.19), 1.54 (95% CI: 0.59-3.98), and 1.79 (95% CI: 0.68-4.69), respectively. Conclusions: Underweight boys were more likely diagnosed with depression than normal weight and overweight boys. While in girls, the probability of depression increased by increased BMI.