"There's always so much going on here," Pahl says.
At home, as a mother of four, Pahl deals with family meals and children's schedules. She cleans up the kitchen, drops off the kids, juggles some office e-mails — and don't forget, the dog needs a walk.
"When you know you've got a long list, you just power through," Pahl says.
Our brains are designed to help us "power through." Under stress, the brain signals to release hormones including adrenaline and cortisol. They give us energy, strengthen the immune system, improve reflexes and even help our memory.
But if we are always under stress, the release of cortisol begins to work against us.
McEwen has discovered that chronic stress causes neurons in the brain to shrink and change shape. In animals, that causes a loss of memory, increased anxiety and aggressiveness that can lead to signs of depression.
Other research, undertaken by psychologist Elissa Epel, has shown how chronic stress can speed up aging and make us more prone to disease.
"Stress has been shown to affect virtually every physiological system we have," Epel says. "Stress even affects cells at the molecular level."
Eppel's research has shown that telomeres, the protective coating at the end of chromosomes, get frayed and worn by stress, mimicking the effects of aging.
In a world that's now filled with cell phones and BlackBerrys, instant messaging and expectations of 24/7, our brains can get a stress signal every time an e-mail comes in. Technology is creating new sources of chronic stress.
"I actually had one of my partners walk into my office, I looked at him and just said, "What? What? What? What now?," Pahl says.
Even those who manage stress well can sometimes be overwhelmed. Those who don't manage stress, psychologist Christina Maslach discovered, can reach a breaking point: burnout.
"When people are experienceing burnout they are more likely to make mistakes make errors," she says. "They don't work as well."
But scientists say the brain's resilience can help prevent burnout.
"The important thing to remember though is when we stop the stress, the neurons will grow back to normal size," McEwen says.
The key is to give the brain time without stress: relaxing with family, exercising, eating well — and sometimes, just sometimes, ignoring those e-mails.