Apathy as a Within-Person Mediator of Depressive Symptoms and Cognition in Parkinson's Disease: Longitudinal Mediation Analyses

Sarah M. Szymkowicz, Jacob D. Jones, Holly Timblin, Cameron A. Ryczek, Warren D. Taylor, Pamela E. May

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Objective: Greater depressive symptoms are associated with worse cognitive functions in Parkinson's disease (PD); however, it is unclear what underlying factors drive this association. Apathy commonly develops in PD and may be a pathway through which depressive symptoms negatively influence cognition. Prior research examining depressive symptoms, apathy, and cognition in PD is limited by being predominantly cross-sectional. This study examined the role of apathy as a within- and between-person mediator for the longitudinal relationships between depression severity and cognitive functioning in patients with early PD. Methods: Participants included 487 individuals newly diagnosed with PD followed annually for up to 5 years by the Parkinson's Progression Marker Initiative. At each visit, participants completed depressive symptom measures, apathy ratings, and cognitive tests. Multi-level structural equation models examined both the within- and between-person effects of depressive symptoms on cognition through apathy, controlling for demographics and motor severity. Results: At the within-person level, apathy mediated the association between depressive symptoms and select cognitive functions (global cognition, attention/working memory, visuospatial functions, and immediate verbal memory; indirect effects, bootstrap p's <0.05). Significant between-person direct effects were found for depressive symptoms predicting apathy (boostrap p <0.001) and lower scores on most cognitive tests (bootstrap p's <0.05). However, the indirect effects did not reach significance, suggesting between-person mediation did not occur. Conclusion: Findings suggest worsening of depressive symptoms over time in patients with PD may be a risk factor for increased apathy and subsequent decline in specific cognitive functions.

Original languageEnglish (US)
Pages (from-to)664-674
Number of pages11
JournalAmerican Journal of Geriatric Psychiatry
Issue number6
StatePublished - Jun 2022


  • Apathy
  • Parkinson's disease
  • cognitive functioning
  • depression
  • mediation
  • structural equation modeling

ASJC Scopus subject areas

  • Geriatrics and Gerontology
  • Psychiatry and Mental health


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