CYP2D6 and Parkinson disease: Together with our data these findings suggest that individuals with a poor metabolizer phenotype resulting from a non-functional debrisoquine 4-hydroxylase enzyme in CYP2D6*4 allele carriers or potentially also from other polymorphisms in the CYP2D6 gene [39] exhibit an increased risk for PD especially when exposed to potential neurotoxins such as pesticides in the intensive agricultural landscapes.