Depression Increases Risk of Cognitive Decline, Dementia

Researchers found that patients with depression were at increased risk of cognitive decline long before dementia could be diagnosed.

Amber John, BSc, MSc

A recent meta-analysis showed that adult patients who experience affective disorders like depression or anxiety may be at higher risk of cognitive decline, long before clinical dementia is diagnosed.

“Although there have been individual studies addressing this question, it is difficult to draw a straightforward conclusion, due to conflicting findings and differences in the specific aims/methods of each study,” lead researcher Amber John, BSc, MSc, a PhD student at the University of Sussex, School of Psychology, told MD Magazine. “As our population gets older, it is becoming increasingly important to identify factors which may play a role in predicting future cognitive health.”

The team compiled 34 longitudinal studies on affective disorders, anxiety and depression, and their relationship with cognitive decline. With some overlap, 32 of the studies covered depression and 5 focused on anxiety.

Many previous studies have examined the association between affective disorders and dementia diagnosis. However, the study authors note that cognitive decline often occurs over decades prior to any diagnosis. In an effort to understand how the disorders impact the general population, they only included studies where no patients were diagnosed with dementia at the outset in the current analysis.

Cognitive symptoms such as impaired memory and executive control are common in affective disorders and are underscored by pathological brain circuitry. Since they did not include patients previously diagnosed with dementia, the meta-analysis relied on studies that measured cognitive state through assessments of overall cognitive function using tests like the Mini-Mental State Examination or other composite assessments that look at multiple functional measures.

They found that patients who experienced depression were at greater risk of cognitive decline over time. The researchers wrote that this emphasized the importance of monitoring the cognitive state of individuals with affective disorders.

“The main finding of our research is that clinically relevant depression, as well as elevated depressive symptoms, are both associated with a greater cognitive decline in older adulthood. These findings highlight the importance of identifying and treating mental health problems as early as possible in order to protect future cognitive health,” said John.

The results for anxiety were less clear. Since there were only 5 studies to include, the researchers were not able to conduct a full meta-analysis but described in a narrative review that 2 of the studies associated anxiety with cognitive decline, while 3 did not.

The team says the next important question to investigate is how early this link between depression and cognitive decline may become apparent. “Can we already see cognitive differences between people with higher life time depressive symptoms and people with lower symptoms as early as in midlife?” asked John.

The study, “Affective problems and decline in cognitive state in older adults,” was published in Psychological Medicine.

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