Third, we analyzed few serum markers, and further studies should examine whether other factors, such as activation of oxidative and nitrosative stress pathways and other cytokines implicated in the pathogenesis of psoriasis (e.g., TNF-α, IL-17A, IL-12, IL-23), are associated with the development of depression in patients with psoriasis. This evidence concerns the gene IL17A and depressive symptom measurement.