Public Health

Area of Science:

• Neuroscience
• Psychiatry
• Gerontology

Background:

• Psychotic symptoms, including delusions, are common in Alzheimer's disease and depression, often linked to worse patient outcomes.
• Cognitive Load Theory suggests depression impairs cognition through rumination, depleting mental resources.
• The mediating role of delusions between depression and cognitive decline is not well understood.

Purpose of the Study:

• To investigate the mediating role of paranoid delusions in the association between depression severity and cognitive outcomes.
• To analyze data from the National Alzheimer's Coordinating Center (NACC) for insights into this relationship.

Main Methods:

• Utilized NACC data from 14,588 participants (March 2015-Dec 2024).
• Assessed cognitive function using the Montreal Cognitive Assessment (MoCA).
• Measured depression and paranoid delusion severity using proxy-reported and self-reported scales, respectively; employed structural equation modeling (SEM) for analysis, adjusting for numerous covariates.

Main Results:

• Higher depression severity correlated with increased delusion prevalence (p < 0.001).
• Depression severity was directly linked to poorer cognitive outcomes (p < 0.001) and indirectly through delusions (p < 0.001).
• Delusions accounted for 19.3% of the total effect of depression on cognitive outcomes, with the SEM model showing excellent fit.

Conclusions:

• Poorer cognitive outcomes in depressed individuals are partly mediated by delusions.
• Further prospective studies are needed to confirm these findings.
• Interventions targeting delusions could potentially enhance cognitive function in patients with depression.