The C/C-T/T and C/A-T/T genotypes of c.-1849C>A – IDO1 (rs3824259) and c.-1668T > A – TPH1 (rs623580) were associated with a reduced risk of stroke, whereas the C/A-T/A and C/A-A/A genotypes caused an increase of the risk in the Polish population. Here, IDO1 is linked to stroke disorder.