Children and adolescents with psychiatric disorders have high relative leptin levels upon adjustment for sex, BMI, and pubertal status.

The relationship between leptin levels and psychiatric disorders has been studied more extensively in adults than in children and adolescents. However, the results are conflicting. We investigated serum leptin levels in children and adolescents (11 to 18.9 years) with psychiatric disorders (n = 363). Absolute and relative (body-mass-index (BMI)-, sex- and pubertal-stage-adjusted z-scores using reference values of healthy children and adolescents) leptin levels of different patient groups according to diagnosis were compared. The association between leptin levels and depression (Beck Depression Inventory-II) and anxiety (Child Behavior Checklist and Youth Self Report) was examined using regression analysis. Leptin z-scores were higher in patients with psychiatric disorders than in healthy controls (median 1.50, p < .001). While global tests suggested differences in leptin z-scores between patients with different psychiatric disorders, these differences could not be attributed to diagnosis groups in post-hoc pairwise comparisons. Absolute leptin levels differed between psychiatric disorders (p < .001). Patients with anorexia nervosa (AN) had the lowest levels, and patients with mood disorders had higher leptin levels than patients with mental disorders other than mood disorders, anxiety or AN. Neither absolute nor relative leptin levels were related to depressive or anxiety symptoms in regression models adjusted for sex and BMI. Significantly elevated BMI-, sex- and puberty-stage-adjusted leptin levels were observed in children and adolescents with psychiatric disorders compared to a reference sample. Further controlled studies are needed to confirm and explain this finding. No relationship was found between absolute or relative leptin levels and symptoms of depression or anxiety.