It has been established in multiple studies that people with a history of depression run a risk twice that of individuals who do not have depression. Those with chronic or recurrent depression run a particularly high risk. The association is there, but research is still not clear as to why this link exists. Finding out the connection could lead to earlier diagnosis and treatment and therefore, better outcomes. This could be a great discovery for millions of people who suffer from two common conditions.
The Chicken and Egg Problem
When it comes to depression and Alzheimer’s there is a dilemma as to which comes first, like in the chicken and the egg problem. Depression is a co-existing condition with Alzheimer’s and is sometimes the first sign that the disease is developing. So, there is a need to separate an episode of depression which is symptomatic of Alzheimer’s from depression that is an early risk factor. It gets even more complicated than this, as depression may also be a symptom of more than one disorder; in fact it can be an indicator of many brain disorders.
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Genetics appear to be important in both disorders, but a genetic risk for depression, for instance, isn’t necessarily a risk for developing Alzheimer’s disease. Cortisol, the stress hormone also plays a key role and is known to be raised in both depression and Alzheimer’s disease. Cortisol may also accelerate cognitive decline and high levels of it are associated with brain damage, including that observed in Alzheimer’s.
Another common denominator between depression and Alzheimer’s is inflammation, further complicating the clinical connection between the two disorders. Inflammatory changes occur in the blood of people with depression and inflammation of the brain is observed in people with Alzheimer’s disease. The question is whether inflammation that causes depression is associated with a higher risk for developing Alzheimer’s. If research can establish what kinds of depression are caused by inflammation, then early interventions might help slow down the process of Alzheimer’s.
The Role of Amyloid
Research has shown the slow and steady accumulation of amyloid is the hallmark of Alzheimer’s disease. Even small amounts of it can impact the relationship between depression and cognitive problems. While not every older adult who has depressive symptoms and amyloid buildup will have cognitive and memory deficits, brain volume, or the hippocampus, the brain’s memory center, may be the missing link between depression and cognitive deterioration. To make this relationship even more complex, other mechanisms including tau protein, inflammation and high blood pressure may all be involved in depression and Alzheimer’s disease. Some experts believe that depression and amyloid work together over time to affect cognitive abilities.
Practically Speaking
While there seems to be a strong relationship between depressive symptoms appearing early on, and the later development of Alzheimer’s, the underlying mechanisms are still unknown. But, if this is truly the case, clinicians may pick up on these signs and begin early intervention for slowing the disease progress or preventing Alzheimer’s altogether. If an older adult’s mood suddenly changes and begins to deteriorate, there may be cause to assess for Alzheimer’s. So, the question remains, is depression a sign of cognitive loss or is the cognitive decline the forerunner of depression?
(NOTE: Interested in learning more about Memory Care & Dementia? Checkout my Memory Care & Dementia CEUs on CEU Academy and try a FREE CEU today!)