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In its most basic form, the stress response is known as "fight or flight," and it swings into action whenever you're confronted with a novel or threatening situation. "If you step off the curb in front of an oncoming bus, your body reacts automatically to protect you,"
In a matter of seconds and without even thinking, you begin pumping out brain chemicals and hormones, including adrenaline and cortisol. Your heart rate accelerates, oxygen-bearing red blood cells flood the bloodstream, the immune system gears up for the possibility of injury, and energy resources are diverted to your muscles, brain, heart, and lungs and away from functions, such as digestion and hunger, that can wait until the crisis has passed.
Meanwhile, the brain releases a cascade of endorphins, the body's natural opiates, to dull the pain of those potential injuries.
You're ready for action, whether it's a full-out battle or a hasty retreat―in this case, fleeing back onto the sidewalk to escape the speeding bus.
When the danger has passed, all these systems are restored to their normal resting state. "Your stress response makes you get out of danger, "Without it, you'd be dead."
Many of the physical changes that energize you to get out of the way of the bus are the same ones at play in positive situations. Your heart races when you're falling in love. Your palms grow sweaty on the first day of a new job. How do you know if it's happiness or stress? You label what you're feeling: Your racing heart and sweaty palms happen first, and then depending on your assessment of the circumstances, you perceive yourself as either excited or happy or stressed. "Our stress isn't a result of the event but of the view we take of it,"
Once you escape the oncoming bus, you're out of danger. Calm returns both physiologically and emotionally: Your pulse slows, the panic subsides, you start to become aware of things like appetite again. All good. But things go awry when stress persists and your body has no opportunity to return to this resting state (or the opposite of the fight-or-flight state). Getting back to normal is much more complicated when the source of your stress is constant and negative, or more conceptual, emotional, or psychological—and when fighting or fleeing a visible threat is not an option: when you're constantly worrying about not having enough money to retire, stuck in a draining relationship, or trapped in a cycle of toxic productivity and burnout.
Simply envisioning being in a traffic accident and/or worrying about it constantly can switch on your stress response without you actually needing to experience a car crash. Anxiety—ruminating on the past, worrying about threatening future scenarios—can activate the stress response and start a vicious loop. And emotional stressors such as frustration with a job or a relationship, which are as powerful as tangible stressors (an earthquake, a shark), are recurring and can accumulate until the fight-or-flight response is constantly ramping up. This build-up overloads us and can start to manifest as physical symptoms—fatigue, irritability, exhaustion. In the most extreme cases, an always-stressed state can lead to more serious health conditions. Unless, that is, you put the brakes on from time to time.
"There's no doubt that the physiology that fuels a chronic stress response can make us sick," Dr. Sternberg says. But stress doesn't "cause" heart attacks or depression in the way a virus causes the flu. How it impacts your body depends in part on your genes. Take an autoimmune disease like rheumatoid arthritis: "There are 20 different genes on 15 different chromosomes that determine whether or not a person will get inflammatory arthritis," Dr. Sternberg says. "If you have all 20 genes, you'll most likely get it. If you have two, you probably won't. If you have five, you may or may not get the disease, and the degree to which your stress response is activated could tip the balance."
Your physiological destiny isn't completely fixed, however. Although we're programmed to develop in a certain way and at certain times, early stressful experiences during childhood (or even before), such as the death of a parent, can alter the way our brains develop and actually change them, as well as impact the immune system and endocrine system, according to Dr. McEwen. As a result, those people tend to be more sensitive to stressors later in life and are more likely to suffer the health consequences.
The dual nature of stress, both protective and destructive, is mirrored in the dual role of cortisol, a hormone central to fight-or-flight. In an emergency, a jolt of physiological chemicals, including cortisol, boosts your immune response―a good thing. Once the emergency has passed, however, it is also cortisol's job to inform the immune system to stand down and return to normal. If too much stress keeps excess cortisol circulating for too long, your immune cells become sluggish and eventually die, leaving you open to infection.
What about the flip side? If too much stress makes you more susceptible to getting sick, can minimizing stress help you heal? Maybe. A lot more research is needed to understand whether coping techniques like mindfulness actually help reverse stress damage at the physiological and biological level. But a growing number of medical facilities have been approaching this question through integrative programs that help patients control illnesses by controlling stress. One of the oldest is the Center for Mindfulness, at the University of Massachusetts Medical School, in Worcester, home of the first Stress Reduction clinic practicing Mindfulness-Based Stress Reduction (MBSR), started by Jon Kabat-Zinn, Ph.D. Here, patients learn mindfulness practices like mindful breathing, yoga, and meditation with the goal of lowering stress.
At the very least, there's no harm in looking for ways to reduce and manage stress if it helps you feel better, right? If you feel chronically overwhelmed, consider these proven ways to get out from under its grip.
