Depression

Depression and Dementia

Depression may accelerate the brain aging process.

Posted Jan 11, 2021

Tim Doerfler/Unsplash
Source: Tim Doerfler/Unsplash

While a decline in cognitive function is an inevitable part of aging, and while affective disorders are also common in older adults, it has been found that depression can actually speed up and worsen declining brain function. John et al. (2018) have found a significant association between depression and cognitive decline.

After conducting reviews on several worldwide longitudinal studies analyzing affective problems and cognitive function, the authors found that depression was a continuous predictor of a significant decline in cognitive state. Additionally, older adults with clinical depression and/or depressive symptoms, as measured by questionnaires such as the Mini Mental State Examination (MMSE) and the Geriatric Depression Scale (GDS), exhibited a greater decline in cognitive ability than those without depression.

These findings corroborate the notion that depression, while detrimental in and of itself, may actually have other unexpected, deleterious effects on health.

As it turns out, affective disorders have recently been associated with an increased risk of developing dementia, both as a risk factor and a prodrome for the condition. This risk of acquiring dementia increased with greater severity and frequency of depressive symptoms (da Silva et al., 2013).

Moreover, patients with depression have been generally found to exhibit alterations in the following areas of cognitive function: affective processing, memory, executive control, and feedback sensitivity. Each of these areas seems to be linked to multiple regions of the prefrontal cortex working in tandem with subcortical regions and temporal structures, such as the amygdala, hippocampus, and the thalamus. For instance, elderly depressed patients have exhibited reduced hippocampal gray matter volume relative to their non-depressed counterparts (Clark, Chamberlain, & Sahakian, 2009). Functionally, this has transpired through compromised working memory, attention, and forward planning seen in major depressive disorder (MDD) (Elliott et al. 1996, Rogers et al. 2004).

It is worth delineating the difference between the findings outlined here and that of ‘pseudo-dementia,’ in which geriatric patients who are being worked up for cognitive impairment are assessed for depression which can manifest with signs of cognitive and memory impairment, and which is resolvable with addressing their underlying depression. What I am outlining here is how the findings here have suggested that depression has been found, in this study, to be associated with a subsequent increased risk for acquiring dementia later on in life.

Intuitively, then, if depression were to be linked to impaired cognition, then treatment with an antidepressant should improve cognitive outcomes. This has been assessed in studies such as a longitudinal study by Shilyansky et al. (2016), in which participants were treated with escitalopram, sertraline, or venlafaxine extended-release antidepressants. For response inhibition, attention, decision-making speed, information processing, and verbal memory, the authors found that, regardless of which antidepressant was used, there was no notable improvement in any of these domains. However, cognitive flexibility (the ability to adapt thinking based on changes in the environment) and executive function were found to improve somewhat with treatment with antidepressants. This suggests that there is a multifactorial effect of depression on cognitive impairment and decline, and that each element of cognition is unique in its response (or lack thereof) to treatment.

At the same time, recent evaluation of another SSRI (selective serotonin reuptake inhibitor) and serotonin receptor modulator, vortioxetine, indicated much better outcomes on multiple cognitive domains, such as processing speed, learning, executive function, and memory, for patients with MDD. This manifested through improved performances on a Digit Symbol Substitution Test and the Rey Auditory Verbal Learning Test. These improvements in cognitive outcomes appear to be independent of its effects on ameliorating depression (Frampton, 2016).

While there is research being conducted in addressing medications, there should be a focus on investigating whether psychotherapy, such as cognitive-behavioral therapy, can improvement not only depression but the cognitive decline that comes with it. As it stands, there is still a scarcity of research investigating the effect of psychotherapy on cognitive outcomes in depressed individuals. This is an avenue that needs to be explored more.

All of this just highlights how complicated addressing cognitive decline actually is, and how much more research is needed to find both an effective pharmacological therapeutic and corresponding psychotherapy to ensure long-term cognitive well-being in patients with depression.

In any case, this finding gives even more support to the fact that depression and mental health conditions must be taken seriously and addressed accordingly. Additionally, with a growing population, and one living longer as well, we need to look after our older population and ensure that their mental health needs are met. Many already have to deal with inevitable issues with physical health due to aging. The last they need is to have to battle depression. Adding on to that the elevated risk of cognitive decline, and worse, dementia, that comes with depression, and we really start to see just how crucial combating mental health really is for the elderly.

References

Clark, L., Chamberlain, S. R., & Sahakian, B. J. (2009). Neurocognitive Mechanisms in Depression: Implications for Treatment. Annual Review of Neuroscience, 32(1), 57-74. doi:10.1146/annurev.neuro.31.060407.125618

da Silva, J. D., Gonçalves-Pereira, M., Xavier, M., & Mukaetova-Ladinska, E. B. (2013). Affective disorders and risk of developing dementia: Systematic review. British Journal of Psychiatry, 202(03), 177-186. doi:10.1192/bjp.bp.111.101931

Elliott R, Sahakian BJ, McKay AP, Herrod JJ, Robbins TW, Paykel ES. (1996). Neuropsychological impairments in unipolar depression: the influence of perceived failure on subsequent performance. Psychol. Med. 26:975– 89

Frampton, J. E. (2016). Vortioxetine: A Review in Cognitive Dysfunction in Depression. Drugs,76(17), 1675-1682. doi:10.1007/s40265-016-0655-3

John, A., Patel, U., Rusted, J., Richards, M., & Gaysina, D. (2018). Affective problems and decline in cognitive state in older adults: A systematic review and meta-analysis. Psychological Medicine, 1-13. doi:10.1017/s0033291718001137  

Rogers MA, Kasai K, Koji M, Fukuda R, Iwanami A, et al. (2004). Executive and prefrontal dysfunction in unipolar depression: a review of neuropsychological and imaging evidence. Neurosci. Res. 50:1–11

Shilyansky, C., Williams, L. M., Gyurak, A., Harris, A., Usherwood, T., & Etkin, A. (2016). Effect of antidepressant treatment on cognitive impairments associated with depression: a randomised longitudinal study. The lancet. Psychiatry, 3(5), 425-35.