Unlocking Dementia’s Role in Mental Illness

Studying the intersection of symptoms of dementia and psychiatric disorders may lead to better treatments for both conditions.

About one in five people over the age of 55 struggles with some type of mental disorder, such as depression or anxiety. And nearly two-thirds of nursing home residents display mental and behavioral problems.

Could brain changes that trigger dementia be fueling emotional and behavioral changes in some of these older adults? Or could depression, for example, be a more significant contributor to dementia than is currently understood? It appears both hypotheses may be true.

Jennifer Gatchel, MD, PhD, a geriatric psychiatrist with Massachusetts General Hospital, believes that psychiatric symptoms may be worsened by the onset and progression of Alzheimer’s disease and other forms of dementia. “These are conditions I see every day in my practice that I find highly compelling,” Dr. Gatchel says. “Could psychiatric symptoms in older adults be driven in part by Alzheimer’s disease pathology and proteins impacting brain circuitry? If so, it would represent an important shift in the way we think about treating older adults presenting with these symptoms.”

The Mood and Memory Relationship

Mood and personality changes are common symptoms of Alzheimer’s disease and other forms of dementia. To better understand how cognitive health and emotional and behavioral health affect each other in our later years, Dr. Gatchel is taking a multi-pronged approach to the subject. In her research, she uses a combination of cognitive testing, clinical assessments that include interviews with family members, and neuroimaging (brain scans).


  • Tell your primary care physician if you notice any changes in your thinking or memory skills, as well as in your mood or behavior. Changes in your sleeping and eating patterns should also be reported.
  • Ask your family members or friends if they have noticed any mood or memory changes. It is often a spouse, child or close friend who observes changes before the individual.
  • Continue to follow a healthy lifestyle, which means getting regular exercise, eating a heart-healthy diet, limiting alcohol consumption, getting enough sleep, getting regular blood work and physical check-ups, and doing brain-challenging activities, such as taking classes, learning new hobbies, traveling, and being engaged socially.
  • Don’t assume that dementia and mood disorders are inevitable parts of aging. Be optimistic. Be healthy. Be aware that if brain changes develop, early treatment can often help slow their progression.

Positron-emission tomography (PET) neuroimaging allows Dr. Gatchel to see amyloid and tau proteins, which are thought to be the building blocks of Alzheimer’s disease. PET uses radiotracers, which are small amounts of radioactive material that are injected into the bloodstream. The radiotracer emits signals (positron emissions), which form gamma rays that are detected by a special camera. A computer takes those gamma rays and creates detailed images of the brain.

PET neuroimaging allows Dr. Gatchel to see the location and amount of tau and amyloid buildup, and then track changes in those proteins over time. As part of her study, Dr. Gatchel can also see how those changes compare with what is observed in those individuals in a clinical setting.

Assessing brain function and mental health involves interviews with the individual and their families about any noticeable changes in their mood or personality, behavior, memory, and day-to-day functioning. Study participants also take cognitive tests that can pick up on even slight changes that could indicate brain degeneration.

Chicken or the Egg?

So is it that dementia contributes to depression and other mood orders, or are they early indications of dementia? It’s a “chicken or the egg” question without a simple answer.

“On the one hand, symptoms of depression or anxiety may be a precursor of Alzheimer’s disease, and may be among the earliest signs of the disease,” Dr. Gatchel says. “On the other end of the spectrum, recurrent episodes of depression may serve as risk factors for dementia. Also, older adults who have a diagnosis of Alzheimer’s disease may experience a reactive depression. It’s a complex question depending on which stage of the disease we’re looking at.”

Research has uncovered some interesting findings in a group of people over the age of 60, with no diagnosed cognitive problems or psychiatric disorders. The group is part of the Harvard Aging Brain Study, led by neurologist Reisa A. Sperling, MD, and radiologist Keith A. Johnson. Dr. Gatchel found that, among people who were still cognitively normal, subclinical depression symptoms were associated with tau accumulation in the parts of the brain most affected by the early stages of Alzheimer’s.

Another group participating in the Harvard Aging Brain Study is a collection of younger people living in Colombia. Dr. Gatchel noted that among the participants who had no cognitive impairment, subclinical symptoms of depression were associated with amyloid accumulation in the brain. One of the next phases of her research is to compare the formation and progress of depression and anxiety in early-onset and late-onset Alzheimer’s. Dr. Gatchel also plans to recruit a group of older adults with more severe psychiatric conditions to study how dementia plays a role, if at all, in their lives. This is important, because participants in the Harvard study were specifically chosen because they did not have severe psychiatric symptoms.

“We may be observing only a modest relationship between depressive symptoms and tau because individuals with more severe depressive symptoms were excluded from the study at entry,” Dr. Gatchel says. “Would we see a stronger relationship if we examined individuals who had more severe depressive symptoms? Would we still observe a relationship with tau as compared to amyloid? Also, if we follow individuals over time, do those with more significant depressive or anxiety symptoms accumulate pathology more rapidly? These are just some of the questions we hope to address in the next phase of work.”

Ultimately, Dr. Gatchel hopes that by better understanding how emotional and cognitive disorders affect one another, individuals at risk for either or both challenges can be identified and treated earlier—hopefully reducing the compounding effects of these two troubling brain problems later on.


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