Studies have shown that caffeine intake is negatively correlated with corpus striatum volume, the availability of DAT in the corpus striatum, and the formation of Lewy bodies, while being positively correlated with nicotinamide adenine dinucleotide (NAD) availability in PD patients, and these studies suggest that caffeine has a potential ameliorative effect on pathological changes and clinical symptoms in PD patients [189,190,191,192]. Here, SLC6A3 is linked to Parkinson disease.