The exact cause of Parkinson’s disease is still unknown. Genetic factors, environmental factors, ageing and oxidative stress may all be involved in the degenerative death process of PD dopaminergic neurons. The incidence and prevalence of PD increases with age, and the onset of PD mostly occurs above the age of 60, suggesting that aging is associated with the onset of the disease. Data show that with age, the nigrostriatal dopaminergic neurons in the brain of normal adults will progressively decrease. However, the prevalence of PD in older adults over 65 years of age is not high; therefore, aging is only one of the risk factors for the development of PD. Ma Jinghong, Department of Neurology, Xuanwu Hospital, Capital Medical University 2. Genetic factors: The role of genetic factors in the pathogenesis of PD has received increasing attention from scholars. Since the discovery of the first Parkinson’s disease causative gene alpha-synuclein (PARK1) in the late 1990s, there are at least six causative genes associated with familial Parkinson’s disease. However, only 5-10% of Parkinson’s disease has a family history, and most are still disseminated cases. Genetic factors are also only one of the factors in the development of PD. 3. Environmental factors: In the 1980s, American scholars such as Langston found that some drug users would rapidly develop typical Parkinson’s disease-like symptoms and were effective with levodopa preparations. It was found that synthetic heroin smoked by drug addicts contains a neurotoxic substance of 1-methyl-4 phenyl-1,2,3,6-tetrahydropyridine (MPTP). This substance is converted to the highly toxic 1-methyl-4phenyl-pyridinium ion MPP+ in the brain and selectively enters nigrostriatal dopaminergic neurons, inhibiting mitochondrial respiratory chain complex I activity and promoting oxidative stress, which leads to degenerative death of dopaminergic neurons. This has led to the suggestion that mitochondrial dysfunction may be a causative factor in PD. In subsequent studies it was also demonstrated that mitochondrial respiratory chain complex I activity is selectively decreased in the substantia nigra in patients with primary PD. The chemical structures of some herbicides and insecticides are similar to MPTP. With the discovery of MPTP, it was realized that some MPTP-like chemicals in the environment could be one of the pathogenic factors of PD. However, only a few of the many drug users exposed to MPTP developed the disease, suggesting that PD may be the result of a combination of factors. 4, Other: In addition to ageing and genetic factors, factors such as traumatic brain injury, smoking and coffee drinking may also increase or decrease the risk of developing PD. Smoking is negatively associated with the occurrence of PD, which has been consistently concluded in several studies. Caffeine also has a similar protective effect. Severe traumatic brain injury may increase the risk of developing PD. In conclusion, Parkinson’s disease may be the result of the interaction of multiple genes and environmental factors.