Memory Loss: It is always Age-Related - Fact or Fiction?

New research shows that stress and depression may cause some forms of memory loss. The research is important because it suggests that not all memory loss is an inevitable part of aging.

If you look at a patient as having irreversible dementia, you wont do anything, says Sonia Lupien, Ph.D., a neuroscientist at Douglas Hospital in Montreal. If you treat the depression, you can stop the increase of cortisol and prevent the memory loss.

Studies show that prolonged depression or stress leads to elevated levels of cortisol, a stress hormone produced by the adrenal glands. This in turn appears to shrink or atrophy the hippocampus, the sea horse-shaped part of the brain associated with many kinds of memory and learning.

The hippocampus is an organ of the brain that is particularly vulnerable to stress and stress hormones, says Bruce McEwen, the head of neuroendocrinology at Rockefeller University in New York.

While cortisol levels normally fluctuate over the course of a day and night, they often soar when a person is faced with a stressful situation, such as a job interview or a school test. Studies have shown that this affects memory. For example, researchers reported in the April 2000 issue of Nature Neuroscience that people taking cortisone pills (which metabolize to cortisol in the body) were not as good at remembering a list of words as people taking placebo pills.

For many people, depression appears to cause similar damage; their cortisol levels remain slightly elevated as long as they are depressed. This moderate but constant drip-drip of the cortisol faucet appears to wear down the hippocampus.

In a review of several long-term studies published in the October 1999 issue of Reviews in the Neurosciences, Dr. Lupien concluded that this process is particularly damaging in the elderly.

But theres no strong evidence that the hippocampus shrinks as a part of normal aging. In one recent study, Yvette Sheline, M.D., a professor of psychiatry at Washington University in St. Louis, used magnetic resonance imaging to measure the hippocampus of 48 women aged 23 to 86, half of whom had a history of clinical depression, half of whom did not.

The women with depression had smaller hippocampi and scored lower on memory tests than the non-depressed group, regardless of age.

We expected to see an effect from aging. Instead we saw significant volume loss only in patients with a history of depression, says Sheline, whose study was published in the June 14, 1999 issue of the Journal of Neuroscience.

Research shows that when depression is treated, cognitive function, including memory, improves. The earlier we can recognize the symptoms, the more likely we are to arrest or slow down the degeneration of the brain, McEwen says.

Still, more studies are needed to fully understand the connection between emotions and memory, cautions Mony de Leon, a psychiatrist and professor at New York Universitys medical school. The cortisol-hippocampus research is an exciting start, he says, but much remains a mystery.

For example, researchers havent yet determined what role, if any, cortisol plays in Alzheimers disease. Studies show all people with Alzheimers have hippocampal damage, but their cortisol production varies.

All of these things remain somewhat foggy, says de Leon. It requires much more extensive investigation.

What is Cortisol?

Lets start with the adrenals, two small glands that lie atop the kidneys. The adrenals have one of the highest rates of blood flow of any tissue with the distinction of containing the highest amount of vitamin C per gram of any tissue in the body. The adrenals secrete the bodys four main stress hormones -- adrenaline, norepinephrine, DHEA and cortisol. These hormones are secreted cyclically, with the highest levels dispatched in the morning and the lowest levels at night. Any disruption in the amount of adrenal output can cause serious health problems.

Cortisol, the bodys principal anti-inflammatory hormone, rises during periods of stress, as we grow older, and during periods of chronic pain. This important hormone also promotes healthy protein synthesis, counter-regulates the activity of insulin, and stimulates beta-2 receptors on bronchial muscles to relax and open airways during asthma attacks. Some of the deleterious effects of cortisol imbalance on health are low energy, muscle atrophy, poor bone repair & increased bone loss, thyroid dysfunction, depressed immune system, poor sleep quality, poor skin regeneration and impaired growth hormone release.