Given that BDNF has been shown to enhance the survival of dopaminergic neurons in animal models of PD (Palasz et al., 2020) and BDNF levels are significantly reduced in patients diagnosed with PD (Jiang et al., 2019), it is plausible that differences in BDNF levels among healthy adults with different levels of religiosity, could partially explain the dose–response relationship with PD risk observed in this study. This evidence concerns the gene BDNF and Parkinson disease.