Cognitive function in depression: longitudinal perspectives
File(s)
Author(s)
Price, Geraint
Type
Thesis or dissertation
Abstract
Background: Cognitive deficits are observed after recovery from depressive episodes. It is not known whether these deficits arise at the time of the depressive episode or were already present before them. It is also unknown whether the association is explained by prodromal symptoms of dementia or residual subclinical depressive symptoms after the episode.
Methods: Data were obtained from a longitudinal cohort study of US residents aged over 50 and their partners, observed every two years for up to 22 years. Periods of elevated depressive symptoms (PEDS) were defined based on an abbreviated version of the Center for Epidemiological Studies Depression scale. A multidomain cognitive composite was derived from measures of episodic memory, working memory, object naming and orientation. Changes in cognitive function were modelled in the same individuals before, during and after PEDS and in individuals who did not experience PEDS, using multilevel linear regression adjusted for potential confounders and the nonlinear effect of ageing. Sensitivity analyses were used to exclude prodromal symptoms of dementia and residual subclinical symptoms.
Findings: Amongst 16,486 participants aged 45 to 94 free of depression and dementia at baseline, including 3,475 with incident PEDS, cognitive function was not significantly poorer before PEDS than amongst participants with no observed depression. In most age groups, after adjustment for the nonlinear effects of age and ageing, as well as sex, education and other covariates, cognitive function was poorer, and declined more rapidly, after recovery from PEDS than before PEDS. The result persisted after exclusion of subclinical symptoms and observations twelve or fewer years prior to an observed onset of dementia.
Interpretation: In older people, periods of depression coincide with an accelerated rate of cognitive decline which continues after the depressive symptoms are resolved.
Methods: Data were obtained from a longitudinal cohort study of US residents aged over 50 and their partners, observed every two years for up to 22 years. Periods of elevated depressive symptoms (PEDS) were defined based on an abbreviated version of the Center for Epidemiological Studies Depression scale. A multidomain cognitive composite was derived from measures of episodic memory, working memory, object naming and orientation. Changes in cognitive function were modelled in the same individuals before, during and after PEDS and in individuals who did not experience PEDS, using multilevel linear regression adjusted for potential confounders and the nonlinear effect of ageing. Sensitivity analyses were used to exclude prodromal symptoms of dementia and residual subclinical symptoms.
Findings: Amongst 16,486 participants aged 45 to 94 free of depression and dementia at baseline, including 3,475 with incident PEDS, cognitive function was not significantly poorer before PEDS than amongst participants with no observed depression. In most age groups, after adjustment for the nonlinear effects of age and ageing, as well as sex, education and other covariates, cognitive function was poorer, and declined more rapidly, after recovery from PEDS than before PEDS. The result persisted after exclusion of subclinical symptoms and observations twelve or fewer years prior to an observed onset of dementia.
Interpretation: In older people, periods of depression coincide with an accelerated rate of cognitive decline which continues after the depressive symptoms are resolved.
Version
Open Access
Date Issued
2026-04-15
Date Awarded
2026-08-01
Copyright Statement
Attribution-NonCommercial 4.0 International Licence (CC BY-NC)
License URL
Advisor
Kivipelto, Miia
Middleton, Lefkos
Ahmadi Abhari, Sara
Publisher Department
School of Public Health
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)