Background Obesity in childhood and adolescence has important health consequences, but its relation to risk of adult depression remains uncertain.

Objective To examine the effect of perceived and actual obesity during childhood and adolescence on prevalence and incidence of adult depression risk.

Methods Cohort study of 91 798 female registered nurses followed longitudinally for 12 years.

Results As compared with lean women of the same age, women in the two highest categories of body shape at age 10 had both higher prevalence (OR=2.59, 95% CI 1.46 to 4.61) and incidence (OR=2.01, 95% CI 1.08 to 3.71) of depression. Similar results were obtained for body shape at age 20 (OR=3.43 for prevalence and OR=2.03 for incidence) and for body mass index (BMI) at age 18 (OR=2.92 for BMI ≥40 kg/m²). These associations remained significant after adjustment for multiple confounders.

Conclusion These results indicate that childhood–adolescence obesity is a strong and independent risk factor for adult depression.