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Can Depression Increase the Risk of Dementia?

Can Depression Increase the Risk of Dementia?

Depression can affect people at any age, whereas dementia often affects older people. Depressive symptoms, particularly clinical depression, are a chief symptom of dementia, but they may also be a significant predictor of dementia later in life.

With depression, the time course also varies significantly, with some people having only brief depression with complete recovery, while others experience remitting and relapsing depression over many years. Chronic depression can occur in certain persons; however, it is uncommon. All of these diverse categories may have varied long-term health outcomes.

The current research indicates the association of depression with increased dementia risk. However, it is still ongoing and needs further investigation.

What does the Research Say?

Scientists have conducted a lot of research to establish a connection between dementia and depression. Although some studies suggest a relationship between Alzheimer’s and depression, it is uncertain if it is a risk factor for the disease, an early sign of neurodegeneration, or a reaction to early cognitive abnormalities. Similarly, some studies have reported that depression symptoms occur soon after the onset of AD rather than before it. Furthermore, some others have indicated that depression has only a mild effect on dementia and does not increase the likelihood of Alzheimer’s.

There is also emerging evidence that depression is associated with cognitive decline. According to a meta-analysis of behavioral and psychological symptoms in cognitively normal middle-aged or older adults, depression was the most consistently related risk factor with behavioral or psychological symptoms and cognitive deterioration in Alzheimer’s patients.

In a study published in the Lancet Psychiatry, the researchers reported that those with growing depression symptoms were consistently associated with a higher probability of getting dementia. On the other hand, those who suffered from depression with less severe but persistent symptoms did not exhibit an elevated risk of acquiring the disease. However, another large-cohort study (with 10,000 participants) has concluded that early-life depressive symptoms did not increase dementia risk.

Both the above investigations discovered that extended depressed symptoms in later life (during the decade preceding dementia onset rather than earlier) are good predictors of increased dementia risk. Other studies have discovered similar links, such as the fact that having depression later in life doubles the risk of acquiring dementia. Furthermore, multiple studies have established that late-life depression might increase the risk of all-cause dementia, vascular dementia, and Alzheimer’s.

Researchers in San Francisco recently tried to investigate the possibility of early adulthood depression as a potential risk factor for dementia. They reported in the published study that depressive symptoms in young adulthood are associated with a 59% higher dementia risk.

A Swedish study evaluated the risk of dementia in individuals with and without depression. The researchers found that those with a depression diagnosis were more likely to develop dementia. The risk of dementia seemed to be the most significant in the first year following a diagnosis of depression. After that, it declined substantially over time but remained elevated for more than 20 years after the diagnosis.

Brain Changes in Dementia and Depression

Some previous studies suggest plausible mechanisms that make depressed people more prone to dementia.

Depressed individuals exhibit hyperactivity in the adrenal gland-stimulating area of the brain. As a result, these glands produce more glucocorticoids (such as the stress hormone cortisol). Higher cortisol levels can cause the impairment of the hippocampus, an area of the brain crucial for memory and cognitive function. Research has also revealed that people with Alzheimer’s may experience hippocampus atrophy.

According to research, other factors contributing to cognitive decline may also be at work. Vascular disease, changes in glucocorticoid steroid levels, hippocampus shrinkage, increased amyloid plaque deposition, inflammatory changes, and nerve growth factor abnormalities are among the possible molecular processes linking depression to dementia.

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