This study aimed to examine correlations between the serum levels of neurotrophic factors, growth factors, and cytokines: brain-derived neurotrophic factor (BDNF) and its precursor (proBDNF), epidermal growth factor (EGF), stem cell factor (SCF), migration inhibitory factor (MIF), S100 calcium-binding protein B (S100B), Tumor Necrosis Factor-alpha (TNF-alpha), and Interleukin 8 (IL-8) with Temperament and Character Inventory dimensions in adolescents diagnosed with mood disorders—major depressive disorder (MDD) or bipolar disorder (BD). The gene discussed is EGF; the disease is bipolar disorder.