As such, the present study was designed to investigate the association between gene polymorphisms of IDO (IDO1 and IDO2, a recently recognized enzyme structurally and functionally similar to IDO1 (19)) and its inducers (including IFN-γ, TNF-α, IL-1β, IL-2 and IL-6) and PSD at 2 weeks after stroke (early-onset PSD), taking into account the role of serum IDO1 levels in the pathophysiology of early-onset PSD. The gene discussed is IDO2; the disease is stroke disorder.