Cortisol: too much of this stress hormone can poison the brain: excess cortisol is linked to hypertension, mood disorders, impaired learning and memory, and other brain ills.
The researchers compared 18 healthy control subjects with 18 individuals who had suffered from an endocrine disease called Cushing's syndrome--which causes an overproduction of cortisol--but whose cortisol levels had returned to normal following medical treatment.
Untreated Cushing's syndrome is linked with a range of memory and cognitive impairments, as well as loss of brain volume. Using brain scans, the researchers found that even though the Cushing's patients had undergone treatment and had normal brain volume, they still had abnormal levels of two metabolites associated with neural damage in a key memory region of the brain called the hippocampus; healthy controls had normal levels of these metabolites. The study authors suggested that the metabolites might be used as early markers to identify and rapidly treat individuals with potentially damaging cortisol levels associated with Cushing's syndrome, certain medications, excessive lifestyle stress or other factors. They theorized that addressing cognitive impairment in the early stages might help prevent the continued progression of brain damage and memory problems.
"While short-term exposure to stress hormones such as cortisol can benefit the brain by, for example, increasing alertness and improving memory, long-term exposure can be harmful, as this study illustrates," says Maurizio Fava, MD, Executive Vice Chair of the Department of Psychiatry at MGH. "Over the past decade or so, research has linked chronic stress to greater risk for many problems that affect the brain, including impaired learning, memory, and cognition, greater risk for Alzheimer's disease (AD), vascular dementia, and high blood pressure, and psychological disorders such as depression, and anxiety.
"These findings illustrate the importance of protecting your brain from the effects of prolonged stress by finding ways to remedy or avoid upsetting situations and learning strategies such as relaxation techniques to help reduce tension and ease distress."
In order to maintain stable functioning in the face of physical and mental stress, your brain normally mounts a two-stage response through a process called allostasis. In the first stage, a rush of chemicals including adrenaline (epinephrine) and noradrenaline (norepinephrine) signals your brain to become hyper-alert, with sharpened perceptions and increased ability to form new memories. Your sensitivity to pain is also lowered. If the crisis continues for more than a few minutes or is perceived as severe, the brain signals the adrenal glands to ramp up defenses by releasing Cortisol, which is a longer-acting stress hormone. Among other things, Cortisol directs more energy-giving glucose to the muscles and away from the brain, reducing learning and memory.
When the perceived threat is over, the second phase of allostasis begins. Your body releases new chemicals to call off the system-wide alert. This second stage is a much slower process that can take hours or even days. However, repetitive or unremitting stress can cause your stress-response system to go haywire. Your body may begin to suffer from the damaging long-term effects of stress-related cortisol and adrenaline and as a result, have difficulty turning on the stress response or turning it off after a crisis has passed. These problems, referred to as allostatic loading, put a crippling burden on the brain and body. Over time, the cumulative wear and tear caused by years of allostatic loading--compounded by your genetic makeup, your personal experiences, and your behavior (smoking, drinking, getting too little sleep)--may lead to cognitive deterioration.
THE STRESSED BRAIN
If stress is severe or prolonged, allostatic loading can do lasting damage to your brain, and may well lie behind symptoms we associate with aging. The changes wrought in the hippocampus by prolonged exposure to excessive cortisol levels actually weaken your ability to recover from stress. The hippocampus is responsible for signaling the adrenal glands to shut down the production of cortisol. As it degenerates, that important feedback loop breaks down, and cortisol continues to be secreted. As levels of cortisol climb, damage to the brain intensifies, and the ability to shut down cortisol production weakens even more.
Scientists have found that long-term exposure to Cortisol reduces the ability of brain cells to communicate with one another by shrinking brain-cell extensions called dendrites that receive messages from other cells. High levels of stress hormones reduce the production of new neurons to replace older, dying cells in the brain. The hippocampus shrinks, as does an area of the brain called the prefrontal cortex, a region associated with problem-solving, emotional regulation, and impulse control. Research has shown that shrinkage of the hippocampus is associated with a higher risk of AD.
IDENTIFYING CHRONIC STRESS
"It's normal to experience occasional stress, but chronic stress that threatens your mental and physical health should be addressed," advises Dr. Fava. "Consider seeing your health care provider if you regularly experience physical symptoms such as rapid heart rate, insomnia, headaches, upset stomach, excessive sweating and sighing, and appetite loss, or stress-related behaviors such as nail-biting, drinking or eating to excess, restlessness, or smoking.
"Negative changes in your mental performance, such as indecisiveness, lack of concentration, and poor memory, or your psychological state, such as increasing feelings of depression, anxiety, anger, or irritability, also may be symptoms of chronic stress."
See What You Can Do for strategis that can help reduce stress, halt destructive changes, and give your brain the chance to mend.
RELATED ARTICLE: WHAT YOU CAN DO
To lower your stress levels, consider using these six strategies suggested by by Dr. Fava:
* Put things in perspective. Most problems are only temporary setbacks.
* Stress-proof your body. Eat right, exercise, get plenty of sleep, cut down on caffeine, slow down and enjoy life.
* Spend time with others. Sharing concerns reduces stress, as does laughter.
* Learn relaxation techniques, such as meditation, deep breathing, or yoga.
* Avoid destructive responses, such as smoking, drugs or dinking to excess.
* Exercise. Regular workouts lower Cortisol levels and promote brain health.
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|Publication:||Mind, Mood & Memory|
|Date:||Nov 1, 2013|
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