Apathy in Lewy Body Disorders: A Position Paper

Apathy is one of the most prevalent and disabling non-motor symptoms in Parkinson's disease (PD) and dementia with Lewy bodies (DLB), collectively referred to as Lewy body disorders (LBDs). It is associated with reduced quality of life, accelerated cognitive decline, increased caregiver burden, and poorer functional outcomes, yet remains underrecognized and undertreated. A Working Group of the International Parkinson and Movement Disorder Society's Non-Motor Symptoms Study Group conducted a comprehensive review of the literature and developed a position paper through iterative expert discussion and critical appraisal of available data. This review aims to provide a structured, expert-informed synthesis of the current evidence on the clinical features, neurobiology, assessment, and management of apathy in LBDs and to define priorities for future research and clinical trials. Apathy in LBDs is a multidimensional syndrome encompassing reward insensitivity, negative affect, executive dysfunction, and auto-activation deficits. Converging evidence implicates dysfunction within distributed frontal-striatal-limbic networks and multi-neurotransmitter systems, including dopaminergic, serotonergic, noradrenergic, and cholinergic pathways. Although several pharmacological and nonpharmacological interventions have been explored, few randomized controlled trials have specifically targeted apathy, and no treatment can currently be considered definitively efficacious. Methodological heterogeneity, inadequate phenotyping, and inconsistent outcome measures have limited therapeutic progress. Apathy should be recognized as a primary clinical and research priority in LBDs. Future adequately powered, mechanistically informed trials using standardized diagnostic criteria and validated outcome measures are urgently needed to advance treatment development. © 2026 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.