Depression and memory function - evidence from cross-lagged panel models with unit fixed effects in ELSA and HRS.

Area of Science:

• Neuroscience
• Gerontology
• Psychiatry

Background:

• Depression is linked to cognitive decline and dementia risk.
• The causal relationship between depression and cognition remains unclear.
• Two hypotheses explored: depression as a cause of cognitive decline, and cognitive decline as a cause of depression.

Purpose of the Study:

• To investigate the directionality of the association between depression and cognitive function.
• To test the aetiological risk factor hypothesis (depression impacting cognition) and the reverse causality hypothesis (cognition impacting depression).

Main Methods:

• Analysis of observational data from two large cohorts: English Longitudinal Study of Ageing (ELSA) and Health and Retirement Study (HRS).
• Utilized cross-lagged panel models with unit fixed effects to assess contemporaneous and lagged effects (up to 8 years).
• Contrasted fixed effects models with random effects models to ensure robustness.

Main Results:

• No evidence found supporting the reverse causality hypothesis (cognition impacting depression) in either ELSA or HRS.
• No evidence found for the aetiological risk factor hypothesis in ELSA.
• Results from HRS indicated that depressive symptoms may influence future cognitive function.

Conclusions:

• Current cognitive function does not predict future depression levels.
• Evidence suggests depressive symptoms may negatively impact future cognition, particularly in older populations.
• The relationship between depression and cognition is complex and potentially unidirectional from depression to cognition.