Prodromal depression and subsequent risk of developing Parkinson's disease: a systematic review with meta-analysis

Aim: Parkinson's disease (PD) is a progressive neurological disorder that predominately affects dopaminergic neurons. We believe that this pooling of data will help to better understand the prodromal nature of depression in PD. Materials & methods: We conducted this study in accordance with PRISMA guidelines 2020. Fifteen eligible articles were shortlisted for final analysis. Risk of bias assessment was also conducted Results: The random-effect model revealed that the risk of subsequent Parkinson's disease in patients with prodromal depression was twice as likely (OR, 2.04; 95% CI, 1.02-4.08) as compared with a healthy population. Conclusion: Our meta-analysis concluded that the subsequent risk of PD is significantly higher in patients with depression as compared with healthy individuals. Plain language summary: Parkinson's disease (PD) is a nervous system disease that predominantly affects neurons of the brain that controls voluntary movement and behavioral processes such as mood, reward, addiction and stress. There is a wide spectrum of problems that can present in patients with PD, however, there are few that can precede the beginning of the illness. Previous studies have evaluated the relation of psychiatric symptoms with Parkinson's disease. However, many aspects need to be studied to understand this relationship. The main emphasis of this systemic review is to establish the association of prodromal depression before the development of PD. Our study showed that there is a strong association between depression and PD and suggests an increased risk of developing Parkinson's disease in formerly depressed patients. Though, it is still unclear if depression is either an early prodromal symptom of PD or a causative risk factor for PD and warrants further studies to determine the causality relationship between the two.