Unraveling the link between mood and cognitive decline

By Naveed Saleh, MD, MS
Published April 26, 2021

Key Takeaways

Most physicians routinely encounter elderly patients, and as a clinician, you’ve likely noticed the strong ties between depression and cognitive impairment in your older patients. Whether you specifically treat cognitive disorders or not, every physician is equipped to monitor the general mood and well-being of their patients. In fact, such anecdotal observations are supported by the evidence and represent important consideration with regard to patient health.

Depression is common in people with Alzheimer disease, according to the Alzheimer’s Association. This depression is especially prevalent during the early and middle stages of the disease. It’s estimated that as many as 40% of patients with Alzheimer disease also have significant depression.

Let’s take a closer look at the tangled relationship between depression and cognitive decline.

Shared symptoms

Identifying depression in someone with Alzheimer’s can be difficult, since dementia can cause some of the same symptoms, according to the Alzheimer’s Association. These include apathy, withdrawal, isolation, impaired thinking, and difficulty communicating the sadness, hopelessness, and guilt characterized by depression.

Of note, depression in those with dementia doesn’t always manifest in exactly the same way. It can be less severe, may wax and wane, may not last as long, and typically lacks any form of suicidal ideation.

Where it all begins

The nascence of depression may occur during a liminal stage between healthy aging and dementia—a period marked by mild cognitive impairment (MCI), according to a review article published in Frontiers in Aging Neuroscience. Although less impaired than those with dementia, patients with MCI complain of some degree of cognitive impairment, and typically exhibit cognitive deficits relative to age- and education-matched contemporaries. For the most part, patients with MCI are functional with minimal compromise of activities of daily living.

The prevalence of MCI is estimated to be between 5.0% and 36.7%, with 11% to 33% of those with MCI manifesting dementia within 2 years. Nevertheless, as many as 50% of MCI patients don’t develop dementia at follow-up appointments. Contributing covariates include gender, age, education, vascular risk factors, hormones, genetics, and comorbidities.

According to the results of the Frontiers in Aging Neuroscience study, 16.9% to 55% of patients with MCI present with depression, compared with 11% to 30% of elderly adults without MCI. These findings are independent of confounders including age, race, and gender. 

As for a possible mechanism, the authors suggested that “vascular factors play an important role in depression within preclinical dementia. In MCI patients, new onset of depression was associated with deep subcortical cerebral white matter hyperintensity severity. Another study noted in the review showed that the cognitive decline was associated with vascular burden (white matter hyperintensity) in remitted geriatric depression patients but neurodegeneration (left hippocampal volume) in MCI patients.”

The psychological weight of depression

In addition to cognitive function, quality of life (QOL) can be impacted by various other factors including physical activity, self-reliance, interpersonal relationships, religiosity, health status, and psychological symptoms.

The authors of a qualitative study published in Psychogeriatrics assessed cognitive functions/depressive symptoms via screening tools and clinical testing, and found that depression can substantially detract from QOL in adults with cognitive decline.

In part, the authors wrote, “Our results demonstrated the frequent comorbidity of cognitive impairment and depressive mood.” They added, “Our study confirmed the significant role of depressive mood in the QOL of the elderly, as depression proved to be a major factor that negatively influences their QOL. The accurate and early detection and adequate treatment of emotional and cognitive symptoms and mental disorders in the elderly is important, because cognitive impairment and especially depressive mood, both contribute to the deterioration of QOL.”

Getting help improves QOL

According to the Alzheimer’s Association, treatment for comorbid depression enhances QOL in those with depression. 

They wrote, “The most common treatment for depression in Alzheimer’s involves a combination of medicine, counseling, and gradual reconnection to activities and people that bring happiness. Simply telling the person with Alzheimer’s to ‘cheer up,’ ‘snap out of it’ or ‘try harder’ is seldom helpful. Depressed people with or without Alzheimer’s are rarely able to make themselves better by sheer will, or without lots of support, reassurance and professional help.”

In particular, support groups are helpful—especially during early stages of the disease, when patients maintain insight into their diagnosis and want to participate in their treatment. For those who may not want to attend groups, counseling can be effective.

Important considerations for these patients include establishing a daily routine, carefully choosing the time of day for challenging activities such as bathing, and ensuring regular exercise. Importantly, small successes should be celebrated, love from family and friends cherished, and pleasures like favorite foods prudently indulged.

As for medications, SSRIs are often employed. Risks and benefits should be carefully considered when prescribing these drugs, with the clinician paying close attention to drug-drug interactions and adverse effects.

Bottom line

Although specialties vary, every doctor should be monitoring the mood and general well-being of their patients. Treating dementia, Alzheimer disease, other cognitive disorders, or depression may not be in your professional wheelhouse, but keep in mind that a referral to a neurologist or psychiatrist can do worlds of good for your patient with MCI or dementia. This benefit can be just as important as the treatment of other pathology. 

Of note, depression is just one of at least a dozen risk factors for dementia. You can read more about it here. Finally, researchers say almost half of all dementia cases can be attributed to a small number of modifiable lifestyle risk factors, including smoking, obesity, physical inactivity, and sleep. To learn more about strategies to prevent cognitive decline, please click here.  

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