Interestingly, in the case of c.-1493G>C – IDO1 (rs10089084) and c.803+221C > A – TPH1 (rs1800532), we observed that the presence of the G/G-C/C combined genotype elevated the risk of stroke development more than 22 times (p = 0.003), whereas the C/C-C/A genotype was associated with a nearly 18-fold increase of the risk in the Polish population (p < 0.001). This evidence concerns the gene IDO1 and Stroke.