Non-motor symptoms of Parkinson`s disease-insights from genetics.

Parkinson's disease (PD) is a neurodegenerative disorder characterized by both motor and non-motor symptoms (NMS). NMS including sleep disturbances, depression, anxiety, and constipation are diverse, can precede motor symptoms, and significantly impact patients` quality of life. The severity and type of NMS vary based on age, disease severity, and motor symptoms, and while some respond to dopaminergic treatments, others may be induced or exacerbated by such treatments. NMS also play a role in differentiating PD from drug-induced parkinsonism and are related to gait dysfunction in both early and advanced stages. Genetic factors play a significant role in the development of NMS in PD, with mutations in genes such as SNCA, LRRK2, PRKN, and GBA being associated with severe and early NMS. Familial studies and identification of susceptibility factors have provided insights into the genetic underpinnings of NMS in PD. Neurobehavioral changes, including cognitive decline, are common NMS in PD, and their genetic basis involves a spectrum of mutations shared with other neurodegenerative disorders. Further research is needed to elucidate the functional implications of these genetic factors and their contributions to the pathogenesis of NMS in PD.