Three main groups of P450s were shown to contain those SNPs: 1) xenobiotics-metabolizing P450s demonstrating the biggest accumulation of highly over-represented SNPs, posing a major role for toxic compounds in the pathogenesis of PD, 2) P450s involved in eicosanoid metabolism, confirming the relation of PD to inflammation and 3) P450s involved in the degradation of cholesterol (CYP46A1, CY7B1, CYP39A1), indicating a prominent role of brain cholesterol metabolism for the risk to develop PD. This evidence concerns the gene CYP46A1 and Parkinson disease.