This perspective summarizes prevalence, diagnostic challenges, putative neurobiology (dopaminergic, serotonergic, noradrenergic systems and HPA axis), validated assessment tools, standard pharmacologic and psychotherapeutic treatments, and emerging methods (DBS, neuroimaging, ecological momentary…

Clinically useful for improving identification and symptomatic management of depression in PD and for informing research on affective circuitry and neuromodulation, but offers limited direct insight into molecular disease-modifying targets for Parkinson's therapeutic discovery.

Depression is a prevalent and disabling syndrome characterized by sustained sadness and/or anhedonia, as well as cognitive and physical symptoms. In Parkinson's disease (PD), depression is both common and clinically challenging due to overlapping symptoms and complex etiologic interactions. Major depressive disorder occurs in approximately 17% of PD patients, while clinically significant depressive symptoms affect over one-third. Both PD-specific and general risk factors contribute to this burden, with the latter playing a greater role. Diagnosis is complicated by symptom overlap, prompting recommendations for an inclusive diagnostic approach and use of rating scales specifically validated in PD. Differentiation from related syndromes such as apathy, demoralization and anxiety disorders is essential for appropriate management. Treatment follows general population algorithms, incorporating pharmacotherapy-particularly selective serotonergic reuptake inhibitors, serotonin and noradrenalin reuptake inhibitors, and tricyclic antidepressants-and psychotherapy such as cognitive behavioral or interpersonal therapy, though adjustments are needed to account for PD-related vulnerabilities. Access to adequate care is often hampered by the lack of mental health specialists with specific expertise in PD. From a research standpoint, PD provides a unique model for studying the neurobiology of mood regulation, implicating dopaminergic, serotonergic, and noradrenergic systems, as well as hypothalamic-pituitary-adrenal axis dysfunction. Emerging methods, including deep brain stimulation, ecological momentary assessment, neuroimaging, and machine learning, are expanding insights into emotional processing and its neurophysiological underpinnings. Clinically, routine screening and evidence-based treatment have improved care. Future research promises to refine diagnostic criteria, optimize therapies, and deepen understanding of affective dysregulation in Parkinson's disease. © 2026 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.