Causal associations between depression symptoms and cognition in a community-based cohort of older adults.

OBJECTIVE To evaluate the temporal association between depression symptoms and cognitive function in older adults over a 4-year period. METHODS Using a longitudinal, cross-lagged, population-based design, we studied depression symptoms and cognitive domains (including processing speed, verbal fluency, face and word recognition, episodic memory, and simple and choice reaction time) in 896 community-dwelling adults aged 70-97 years. RESULTS Cross-lagged structural equation models suggested that initial depression symptoms affected subsequent processing speed and simple and choice reaction time but that cognition did not predict depression symptoms over time. The associations between depression and cognitive variables were attenuated when the models were adjusted for sensory impairment, physical health, and locus of control. CONCLUSION The findings suggest that, causally, depression precedes cognitive impairment in this age group and that the association is related to physical health and perceptions of a lack of control.