The idea that hormones have an enormous impact on the brain is the subject of exciting new research. Scientists have long understood that circulating sex hormones shape the hippocampus, that part of the brain essential for remembering daily events and for certain forms of learning, during early brain development. Only recently have they come to realize that hormones, such as estrogen, and stress hormones, including cortisol, also help shape adult brains.
This is good news-bad news.
Long-term chronic stress hormones are bad for the brain, say researchers. Its not just because such stress can make you uncomfortable, anxious, depressed, or fatigued.
Recent research reveals that persistent stress can actually alter the very structure and functioning of your brain cells. The blunt truth: “Stress causes brain damage,” says a leading brain authority, neuropsychiatrist Richard Restak, M.D. of the George Washington University School of Medicine and Health Sciences.
Stress triggers the “fight or flight syndrome,” a primitive response that releases stress hormones (corticosteroids and adrenaline), mobilizing the body to save itself from danger, such as a roaring lion in the jungle. Today as then, short-lived stress may be good for brain functioning. The stress of taking a test, for example, can stimulate a burst of adrenaline that improves memory.
But long-lasting, inappropriate stress triggered by everyday events, such as work frustration, traffic jams, and financial worries can wear your brain down, eroding important neuronal connections, eventually bringing on forgetfulness. Research suggests that chronic stress can actually shrink the hippocampus, the memory center of the brain.
Animal studies by renowned authority on stress and the brain Robert Sapolsky, professor of neuroscience at Stanford, show that a couple of weeks of exposure to elevated glucocorticoid levels cause neuronal dendrites to shrivel up, impairing message transmission. The good news: When glucocorticoid levels subside, dendrites can grow back.
However, years of bathing in glucocorticoids from chronic stress may cause nerve cells responsible for memory to die.
The loss looks for all the world like the death of neurons after a stroke or seizures, says prominent neuroscientist Dr. Bruce McEwen of Rockefeller University. Stress also leads to the creation of free radical chemicals that can cause brain cells to atrophy and die.
Estrogen: The Memory Molecule
In contrast, many researchers believe the hormone estrogen is a potent preserver of memory in older women and possibly a partial antidote to Alzheimer’s disease. Dr. David Snowdon, brain researcher at the University of Kentucky, calls estrogen the number one candidate” for women seeking neuronal protection. “I recommend that older women take estrogen if they can,” agrees Dr. Marilyn Albert, Harvard brain researcher.
Evidence of estrogen’s brain benefits, notably for maintaining and restoring memory, has been accumulating for the last two decades. A recent breakthrough study by Barbara Sherwin at McGill University showed that women whose ovaries were removed, drying up supplies of estrogen, scored lower on cognitive tests, especially in verbal memory. Those who later got estrogen regained all their mental skills. Those denied estrogen in the double-blind trial did not.
New research also shows that estrogen rejuvenated memory centers in the brains of elderly women. When the women were taking estrogen, brain scans revealed “activation” patterns in short-term memory regions that resembled those in the brains of younger women. The dose was 1.25 milligrams daily.
Further, research at Columbia University found that postmenopausal women who had used estrogen replacement for ten years had one third the risk of developing Alzheimer’s disease as women who never took it. Not a single woman who took estrogen replacement during the five year study developed Alzheimer’s disease. Nationwide tests are underway to see if estrogen will delay or reverse mental deterioration in Alzheimer’s patients.
How does estrogen work? Several ways, according to much research. Its known that estrogen increases the activity of neurotransmitters, notably acetylcholine, that are deeply involved in memory. Estrogen also stimulates the growth of dendrites and synapses in nerve cells, enhancing communication channels.
Further, recent research identifies estrogen as a strong antioxidant that shields brain cells from destruction by free radical chemicals. Cell studies show that estrogen reduces the ability of brain cell toxins, such as glutamate and a protein called beta amyloid found in Alzheimer’s brains, to generate destructive free radicals.