Leptin and its association with somatic depressive symptoms in patients with the metabolic syndrome

Background: This study aimed to determine the association between circulating leptin levels and total depressive symptoms as well as depressive symptom dimensions (cognitive and somatic) after controlling for important confounding factors. Methods: The study sample was comprised of 135 participants with the metabolic syndrome. Depressive symptoms were measured using the Beck Depression Inventory - II. Leptin was measured using a leptin-specific enzyme immunoassay. Inflammation was assessed using C-reactive protein and interleukin-6 levels. Results: Leptin was significantly associated with somatic depressive symptoms (β = 0.33, P = 0.018), but not total depressive symptoms (β = 0.27, P = 0.067) or cognitive depressive symptoms (β = 0.21, P = 0.182), after controlling for age, gender, body mass index, and insulin resistance. Further adjustment for C-reactive protein and interleukin-6 levels did not alter the relationship (β = 0.32, P = 0.023) between circulating leptin levels and somatic depressive symptoms. Conclusions: Leptin is independently associated with somatic depressive symptoms in patients with the metabolic syndrome.