Forward MR analyses revealed more cathepsin B (CTSB) associated with less PD risk (OR = 0.898, 95%CI: 0.834–0.966, p = 0.004), while more cathepsin H (CTSH) (OR = 1.076, 95%CI: 1.007–1.149, p = 0.029) and more cathepsin S (CTSS) (OR = 1.076, 95%CI: 1.007–1.150, p = 0.030) associated with increasing PD risk. The gene discussed is CTSB; the disease is Parkinson disease.