Apathy in Neurodegenerative Diseases: Recommendations on the Design of Clinical Trials

Apathy is a common feature of neurodegenerative disorders but is difficult to study in a clinical trial setting due to practical and conceptual barriers. Principal challenges include a paucity of data regarding apathy in these disorders, an absence of established diagnostic criteria, the presence of confounding factors (eg, coexisting depression), use of concomitant medications, and an absence of a gold-standard apathy assessment scale. Based on a literature search and ongoing collaboration among the authors, we present recommendations for the design of future clinical trials of apathy, suggesting Alzheimer disease and Parkinson disease as models with relevance across a wider array of neuropsychiatric disorders. Recommendations address clarification of the targeted study population (apathy diagnosis and severity at baseline), confounding factors (mood/cognition, behavior, and treatment), outcome measures, study duration, use of comparators and considerations around environment, and the role of the caregiver and patient assent. This review contributes to the search for an optimal approach to study treatment of apathy in neuropsychiatric disorders.