Abstract
Background and aimThis study assessed the association between depressive symptom severity and cognition in middle-to-older aged adults with mild-to-moderate depression and cardiovascular risk factors using an online test battery (CogState) and whether changes in depressive symptoms over 3 months were associated with changes in cognition.MethodsParticipants (mean age = 57.8) with cardiovascular risk and mild–to-moderate depressive symptoms completed measures of psychomotor speed, learning, and executive function prior to (n = 445)_and after (n = 334) online depression or attention control interventions. The symptom severity-cognition relationship was examined both cross-sectionally and prospectively.ResultsParticipants exhibited significantly reduced psychomotor speed and variable impairments on measures of learning and executive functioning relative to normative data. However, there was no association of depression severity with cognition at baseline or of change in depressive symptoms with change in cognitive performance.LimitationsParticipants were well-educated, which may have protected against cognitive decline. Attrition may limit generalisability, though is unlikely to explain the lack of association between depression symptoms and cognition.ConclusionsAdults with comorbid mild-to-moderate depressive symptoms and cardiovascular risks performed less well than age-matched normative data on three online cognitive tests; however, we were unable to show any symptom-cognition association cross-sectionally or longitudinally, despite significant improvements in depressive symptoms. This challenges the generalisability of such associations found in more severely unwell clinical samples to those with a broader depressive symptom profile, or suggests that underlying cardiovascular disease may account for the association seen in some clinical studies. This has implications for scaling up selective prevention of cognitive decline.
Highlights
It is recognized widely that Major Depressive Disorder (MDD) is associated with cognitive dysfunction [1,2,3] including impaired learning, working memory, processing speed, and executive functions [4,5,6]
Adults with comorbid mild-to-moderate depressive symptoms and cardiovascular risks performed less well than age-matched normative data on three online cognitive tests; we were unable to show any symptom-cognition association cross-sectionally or longitudinally, despite significant improvements in depressive symptoms. This challenges the generalisability of such associations found in more severely unwell clinical samples to those with a broader depressive symptom profile, or suggests that underlying cardiovascular disease may account for the association seen in some clinical studies
Does improvement in depression result in a significant improvement in cognitive function? The observed cognitive dysfunction of MDD often persists despite reductions in depressive symptoms [13, 14], and any improvements may not reach the levels of cognition that existed prior to onset of the depressive episode; the “scar hypothesis” [13, 15, 16]
Summary
It is recognized widely that Major Depressive Disorder (MDD) is associated with cognitive dysfunction [1,2,3] including impaired learning, working memory, processing speed, and executive functions [4,5,6]. Is the depression severity-cognition association present only in the small group with diagnosed MDD or is it applicable to the much larger group with mild to moderate depression symptoms?. The observed cognitive dysfunction of MDD often persists despite reductions in depressive symptoms [13, 14], and any improvements may not reach the levels of cognition that existed prior to onset of the depressive episode; the “scar hypothesis” [13, 15, 16]. This study assessed the association between depressive symptom severity and cognition in middle-to-older aged adults with mild-to-moderate depression and cardiovascular risk factors using an online test battery (CogState) and whether changes in depressive symptoms over 3 months were associated with changes in cognition
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