More specifically, BDNF Val66Met polymorphism is associated with cognitive processes [112,123,124,125,126,127], and cognitive impairment in neurodegenerative disease, such as Parkinson’s disease (PD) [128,129] and AD [130,131], and even more with several brain disorders, including MDD and bipolar disorder [132,133,134,135,136,137], epilepsy [138,139,140], schizophrenia [125,141,142,143,144], aging and dementia [145] and stroke [117,146,147]. The gene discussed is BDNF; the disease is Parkinson disease.