Depression in Parkinson's disease: Conceptual issues and clinical challenges

Background: Depression frequently accompanies Parkinson's disease (PD) and may have a negative impact on activities of daily living, cognitive performance, and quality of life. Because of the symptom overlap between the 2 disorders, it may be difficult to recognize depression in PD. Moreover, the partially shared pathophysiology may make it difficult to treat depressive symptoms without influencing motor or cognitive function. Objective: To review the current knowledge of the epidemiology, etiology, pathophysiology, and treatment of depression in patients with Parkinson's disease. Method: Discussion of recent studies and relevant literature. Conclusion: Not only conceptually but also in terms of etiology, pathophysiology, and treatment, the relationship between PD and depression remains a challenge. There are still many questions to be answered. In the therapeutic domain, large, placebo-controlled trials are necessary to evaluate the efficacy of antidepressant treatment and allow the development of evidence-based guidelines.