Can Stress Cause Alzheimer's?

Alzheimer’s is a neurodegenerative disorder that starts most commonly in old age. Many studies conducted on animals have suggested that stress can cause Alzheimer’s and worsen its progression. However, whether it causes Alzheimer’s in humans is yet to be established.

Alzheimer’s is a neurodegenerative disorder that starts most commonly in old age. It is the most common cause of dementia (memory loss) and the sixth leading cause of deaths in the United States.

Many studies conducted on animals have suggested that stress can cause Alzheimer’s and worsen its progression. However, whether it causes Alzheimer’s in humans is yet to be established.

A few theories have been proposed that suggest stress plays a role in the development of Alzheimer’s.

Activation of hypothalamus–pituitary–adrenal (HPA) axis

Stress activates the HPA axis that stimulates the release of the stress hormone cortisol from the adrenal gland. Cortisol is an important hormone that is secreted in response to fear and stress. However, if the body is exposed to persistent or chronic stress, high cortisol levels can affect the immune system of the body. They can alter various physiological processes and make you prone to depression, anxiety and early-onset dementia. They can directly affect the pathological processes of Alzheimer’s. Cortisol, in excess, is found to damage the memory center of the brain. High levels of cortisol may reduce the ability to learn and retain new information (this is called short-term memory loss).

Deposition of beta-amyloid in the brain

Alzheimer’s is characterized by increased levels of beta-amyloid, a toxic protein that causes plaque buildup in the brain. Animal studies have reported that stress increased the production of toxic beta-amyloid in animals with Alzheimer’s. There was also a decline in cognitive functioning in these animals.

All the studies evaluating the role of stress in the development of Alzheimer’s have been conducted in animals. These studies have strongly suggested stress as a potential risk factor for Alzheimer’s. Human studies to substantiate the same are lacking. Studies targeting cortisol and beta-amyloid levels have been shown to be effective in animal models of Alzheimer’s. However, when similar experiments were conducted in humans, only a modest effect was observed.

Scientists have suggested that behavioral, psychological or pharmacological strategies aimed at increasing resilience to stress might delay the onset or slow the progression of Alzheimer’s.

Some drugs that seem to work in animals have not been successful in treating humans. It is not known how much stress is required to cause Alzheimer’s. Moreover, how everyone perceives and copes with stress differs considerably. Therefore, more studies in humans are required before saying that stress affects Alzheimer’s. There may also be other causative factors at play. Human studies are also necessary to find out if anti-stress therapies can be used to treat Alzheimer’s.