LEP and major depressive disorder: Briefly, the role of appetite hormones and mood disorders is complex and may differ between disorders.147 For example, Cordas et al showed that reduced leptin is present in depression, especially atypical and bipolar depression; additionally, leptin is associated with current depression.148 Conversely, Pasco et al showed that leptin is elevated in women with a history of unipolar major depression and elevated leptin predicts future depressive disorder.149