IDO1 and stroke disorder: Increased serum IDO1 levels in stroke patients carrying the T allele but not homozygous C allele of the rs9657182 conveyed a liability to early-onset PSD, and in combination with the evidence on the contribution of the T allele to early-onset PSD formation, it could be assumed that the polymorphism in the IDO1 gene promoter region at position rs9657182 affected the expression levels of IDO1 in response to cytokines stimulation following stroke, giving rise to the development of early-onset PSD.