Before the COVID-19 pandemic, depression was already the leading cause of disability worldwide, and its reach only widened during many months of lockdowns and social isolation. According to the World Health Organization, the pandemic spurred a 25% increase in global prevalence of depression and anxiety. An estimated 280 million people around the world have depression, accounting for 3.8% of the global population.
The effects of depression, however, can go far beyond worsened mood. Pain, inflammation, fatigue, headache, and even risk of heart disease have been linked to the illness, as have cognitive impairments. In the Diagnostic and Statistical Manual of Mental Disorders (DSM), cognitive disorders are listed as core symptoms of depression. Its criteria for major depressive disorder include impairments in thinking, concentration, and decision making, demonstrating a strong link between cognition and the mood-related symptoms typically associated with the condition.
The impact of depression on cognitive domains
A number of the processes that constitute human cognition can be affected by depression, including:
- Attention and focus: Out of all the potential cognitive side effects of depression, diminished attention and focus are perhaps the most widely recognized. Depressed patients often report distractibility and an inability to concentrate, both of which can affect their ability to participate in the workplace or school. Clinicians attempting to determine whether attention and concentration deficits are the result of depression should first rule out pre-existing attention deficit disorder or side effects from anti-depression medications.
- Memory: Patients experiencing depression can also suffer from memory loss, although the relationship between the two is not entirely understood. Pattern separation, or the delineation of similar events in the mind, has been shown to be negatively influenced by depression. Depression is also tied to reduced performance in declarative memory, or the intentional remembering of facts.
- Executive functioning: Executive functioning—including the ability to complete tasks, plan, and make decisions—can suffer due to depression. Compared to a healthy control group, students with depression, stress, and anxiety demonstrated impaired decision making.
Unfortunately, it’s not uncommon for cognitive impairments like those above to continue after other symptoms of depression have subsided. The most common antidepressants—Lexapro, Zoloft, and Effexor—have shown to be largely ineffective in combating depression-related cognitive decline. According to one study, 95% of patients saw no improvement in cognitive function even after successful treatment of mood symptoms on these medications.
Given this understanding, new multimodal antidepressants are emerging that treat cognition and function. At the moment, cognitive behavioral therapy and cognitive remediation therapy are thought to be effective methods of treating depression-related cognitive issues.
A prodromal stage of dementia
There’s a considerable amount of debate surrounding the nature of depressive cognitive impairment, especially concerning its relation to dementia. Depression-related cognitive impairment has been referred to as pseudodementia by some researchers, but it has yet to be included in the classification system for dementia.
For elderly patients, depression has been shown to double the risk of eventual dementia onset. While only 18% of depressed elderly patients with strong cognitive health developed dementia, 70% of those with depressive pseudodementia eventually develop dementia.
Still, not all depression-related cognitive impairment is a prodromal stage of dementia. More and more research indicates that younger adults can be impacted by cognitive impairment. A study of adults under the age of 65 with major depressive disorder found that 38% meet the criteria for cognitive impairment in one domain, and 20% in two or more.
MoCA for depression
According to clinical psychology researcher Maria Semkovska, PhD, at the Health Research Institute, University of Limerick in Ireland, it’s not uncommon to see patients who no longer meet the clinical criteria for depression but find their cognitive function and work is still suffering after recovery.
“I believe that after recovering from a depressive episode, cognitive function needs to be assessed routinely before returning to normal everyday life to prevent these negative effects of persisting cognitive difficulties impacting on psychosocial recovery,” Semkovska told Medpage Today. “Even if no treatment could be implemented and/or if issues are minor, it is better to be aware of one’s objective cognitive function before returning to normal everyday life.”
Recognizing the importance of testing for cognitive impairment, researchers have successfully used MoCA to identify its presence in patients with depression. The following studies demonstrate MoCA’s efficacy in revealing depressive cognitive impairments and more:
- “We found that the MoCA total score is able to predict the presence of suicidal ideation in depressed elderly patients in a fair-to-good manner. As late-life depression is already established as a potential prodrome of dementia, longitudinal follow-up may determine whether depressed individuals with suicidal ideation are at higher risk of converting to dementia.” Researchers administered MoCA and several mental health indexes to elderly participants to assess their cognitive abilities. They found that participants dealing with suicidal ideation performed worse on the MoCA than those who weren’t, pointing to MoCA’s potential to predict suicidal tendencies in elderly patients.1
- “After ECT, the MoCA and MMSE total scores were comparable, but the MoCA detected more impairments than did the MMSE for visuo-executive, memory and language subscores.” Researchers sought to determine whether MoCA could help evaluate the cognitive states of patients receiving electroconvulsive therapy (ECT) for depression. They found that MoCA was a useful tool for monitoring cognitive function during ECT and detected more patients with cognitive deficits than the MMSE.2
- “Present findings confirm available evidence about patterns of cognitive impairment in mood disorders, in terms of prevalence and persistence beyond remission in most severe cases. Moreover, a longer DUI was associated with worse cognitive performance during depression, and consequently with poorer outcome, underlining the importance of prompt treatment of these disorders also in light of a cognitive perspective.” Setting out to determine how cognitive impairment evolves in patients with major depressive disorder or bipolar disorder, researchers administered MoCA to patients during a major depressive episode and after remission. Comparing the scores, they found that 50% of the sample met the criteria for mild cognitive impairment during the episode. They also witnessed improved cognition after remission, although some effects still lingered, and observed a relationship between the duration of untreated illness (DUI) and poor cognitive performance.3
- “In this naturalistic sample of patients with TRD in our clinical service, repeated ketamine infusions significantly decreased depression symptoms without impairing cognitive performance. The baseline cognition may positively predict antidepressant responses of repeated ketamine treatment.” Researchers conducted a retrospective chart review to determine the impact of repeated ketamine infusion treatments on neurocognition in patients with treatment resistant depression. They used MoCA to monitor cognitive effects and the 16-item Quick Inventory of Depressive Symptomatology-Self Report Scale to assess depressive symptoms, and found no evidence of cognitive impairment.4
By screening for potential cognitive effects of depression, clinicians can identify impairment and treat patients for the full spectrum of their condition. In turn, patients can more quickly re-engage in their occupations, relationships, and daily lives.
In addition to depression, MoCA can screen for dementia, diabetes, heart disease, early-onset Alzheimer’s, and more—and supports a range of languages and formats. Learn more on our website.
- Stéphane Richard-Devantoy, Icoquih Badillo-Amberg, Kyle T. Greenway, Maria Di Tomasso, Gustavo Turecki, J.A. Bertrand, Low MoCA performances correlate with suicidal ideation in late-life depression, Psychiatry Research, Volume 301, 2021, 113957, ISSN 0165-1781, https://doi.org/10.1016/j.psychres.2021.113957.
- Rémi Moirand, Filipe Galvao, Maxime Lecompte, Emmanuel Poulet, Frédéric Haesebaert, Jerome Brunelin,Usefulness of the Montreal Cognitive Assessment (MoCA) to monitor cognitive impairments in depressed patients receiving electroconvulsive therapy, Psychiatry Research, Volume 259, 2018, Pages 476-481, ISSN 0165-1781, https://doi.org/10.1016/j.psychres.2017.11.022. (https://www.sciencedirect.com/science/article/pii/S0165178117315834)
- Cesare Galimberti, Monica Francesca Bosi, Martina Volontè, Francesca Giordano, Bernardo Dell’Osso & Caterina Adele Viganò (2020) Duration of untreated illness and depression severity are associated with cognitive impairment in mood disorders, International Journal of Psychiatry in Clinical Practice, 24:3, 227-235, DOI: 10.1080/13651501.2020.1757116
- Dai, D., Miller, C., Valdivia, V. et al. Neurocognitive effects of repeated ketamine infusion treatments in patients with treatment resistant depression: a retrospective chart review. BMC Psychiatry 22, 140 (2022). https://doi.org/10.1186/s12888-022-03789-3