The main findings in our study included: (1) Compared to HCs, PD patients had lower serum BDNF levels and higher PHQ-15 scores that could be improved after 8 weeks’ escitalopram treatment; (2) PD patients with higher baseline STAI state, STAI trait, and PDSS-CV scores, but lower serum BDNF levels could present severe somatic symptoms; (3) State anxiety, panic severity per se, and serum BDNF levels contributed to the prediction of PHQ-15 changes post-escitalopram treatment in PD patients. This evidence concerns the gene BDNF and anxiety disorder.