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Depression and Dementia – a complicated relationship


We often hear people say, “I am so depressed” or “that news is so depressing.” These expressions describe a short-lived emotion. Long-lasting or multiple episodes of persistent sadness that affect your feelings, thoughts, and behavior - or clinical depression - can affect your risk for developing or accelerating cognitive impairment and possible Dementia. Clinical depression generally requires long-term treatment.


Alongside sadness, symptoms include feelings of hopelessness, worthlessness, guilt, decreased energy, difficulty making decisions, changes in sleep habits, significant weight loss or gain, and persistent headaches. Considering the symptoms, it should not be surprising that depression can lead to other health complications.


So, how are physical changes in the body and brain related to mood and emotional states? There are several factors at play, among them are neuronal growth and communication, brain size and structure, genetic makeup, and hormones. Changes in these physical factors alter the efficiency or even successful delivery of messages to areas of the brain responsible for emotion, mood, cognition, and more. (1)


Since the brain is made of billions of neurons - specially designed cells that send and receive signals - their abundance and structure regulate neural pathways. While the hippocampus region of the brain is instrumental in moving memories from short to long term storage, it also regulates the abundance and growth of neurons. Changes to its size and structure creates a web of effects. Meanwhile, the thalamus a structure within the brain links feelings to sensory input, building emotion-based reactions to a stimulus. These linkages, dependent upon those messages relayed through neurotransmitters, are responsible for physiological responses to the emotion. (1)


When sensory information is received by the different regions of the brain, the endocrine system is activated, and hormones deliver messages to targeted organs of the body. Stress hormones produce physiological changes, most often an inflammatory response, to every real or perceived threat to your body. In women, fluctuations of ovarian hormones influence her susceptibility to stress, changes in brain structure and function, as well as inflammatory activity. Exhaustion and depression may result when too little thyroid hormone is produced, a result of dysfunction in neural messaging, endocrine response, or both. (4)


The production, transport, and availability of receptors for each type of hormone is dependent upon proteins synthesized as directed by one’s genetic makeup. Genetics also influences a person’s temperament, outlook, and general resilience to life’s challenges. (1) One thing is clear from all of this, depression is complicated.


As the subject is studied, a relationship between depression and risk for Dementia has emerged. Evidence concurrently suggests depression is one of the first symptoms of Dementia and that it can accelerate transition between normal cognition to mild cognitive impairment (MCI) and on to Dementia. (2)


Consider how the physical factors that produce depressive symptoms may worsen in response to disease processes associated with Dementia. Amyloid plaques, decreased brain blood flow, and misconfigured proteins - the “bad actors” - further interrupt neuronal communication and downstream responses to sensory input. On the flip side, these physical factors of depression may set the stage for progressive cognitive impairment by breaking down neuronal and hormonal pathways.


For those already living with MCI, as the severity of symptoms and frequency of episodes increases, so does the risk of developing all-cause Dementia. A 14% increase in risk for each depressive episode has been observed. (2) Specifically, bouts of clinical depression in mid-to late-life can increase the risk of developing Dementia by a factor of two or three.


About one-third of people living with any Dementia type experience depressive symptoms. It is worth noting that nearly 50% of those living with Vascular Dementia will experience depression. (2) Because clinical depression can accelerate or worsen Dementia symptoms, treatment should be a priority. One particularly hazardous behavior that worsens with depression is elopement and critical wandering situations where an individual becomes lost to their caregiver. (3)


Treatment comes in combinations of psychotherapy and medication. Healthy lifestyle habits can both reduce the risk of depression and relieve its symptoms. A healthy diet, regular exercise, social interaction, providing for fun, relaxation, and low-stress living will benefit emotional and physical health.


The risks and concerns are not reserved for the individual living with cognitive impairment. The work of a caregiver can be extraordinarily stressful, time-consuming, and can lead to less than optimal lifestyle habits that increase the risk for depression. Take time for yourself, look to others for support, and monitor your own well-being so that you and your loved one living with Dementia can thrive even under challenging circumstances.


Notes:

(1) Harvard Health Publishing. What causes depression? Onset of depression more complex than a brain chemical imbalance. June 24, 2019. Accessed August 25, 2021 at https://www.health.harvard.edu/mind-and-mood/what-causes-depression

(2) Dafsari, F.S., Jessen, F. Depression—an underrecognized target for prevention of Dementia in Alzheimer’s disease. Transl Psychiatry 10, 160 (2020). https://doi.org/10.1038/s41398-020-0839-1

(3) Jeong, Jae Gwon et al. “A Relationship between Depression and Wandering in Community-Dwelling Elders with Dementia.” Dementia and neurocognitive disorders vol. 15,1 (2016): 1-6. doi:10.12779/dnd.2016.15.1.1

(4) Slavich, G. M., & Irwin, M. R. (2014). From stress to inflammation and major depressive disorder: a social signal transduction theory of depression. Psychological bulletin, 140(3), 774–815. https://doi.org/10.1037/a0035302


Contributor: Karen R. Ogden, team member, Dementia Society of America.


The opinions expressed by contributing authors are not necessarily the opinions of the Dementia Society, Inc. We do not endorse nor guarantee products, comments, suggestions, links, or other forms of content contained within blog posts that have been provided to us with permission, or otherwise. Dementia Society does not provide medical advice. Please consult your doctor. www.DementiaSociety.org