In PD patients, the correlations between NPY and 5-HIAA and CGRP and 5-HIAA were r = 0.50 and r = 0.06; in PD patients with comorbid depression, they were r = 0.25 and r = 0.26 and in MDD patients, they were r = −0.14 and r = −0.47. This evidence concerns the gene NPY and Parkinson disease.