We are born with miraculously integrated bodies and minds. Our lungs draw in vital oxygen, essential for producing energy. Our hearts ceaselessly pump blood through vast networks of vessels to all of our tissues and organs. Raw materials are transformed into fuel by our digestive systems. Our muscles and bones propel us through the world, allowing us first to stand, then walk, then play and work.

Each day our brains take in a barrage of new information, filtering it, selectively storing it, and adapting their way of working accordingly. At the end of each day, we recharge and reset our systems by sleeping. All of us come equipped with a self-contained set of tools that, properly used, may allow us to live 100 years, or maybe even longer.

Beginning early in our lives, though, our genes, our environment, our culture, and our own free will conspire to test this marvelous organism—sometimes to the breaking point. There are people who maintain their health and live long, fruitful lives, sustaining minimal wear and tear. But others—perhaps most of us—push our bodies to the limit. Instead of eating the way our bodies were designed to eat, we indulge in foods filled with sugars and other refined carbohydrates, trans fats, and unhealthy food additives. Instead of walking to nearby destinations, we drive our cars. We sit most of the day. Some of us smoke. Some of us drink too much. Many of us allow negative feelings and stress to rule our thoughts. Not many of us get adequate sleep. The wrong choices trap us in a lifestyle that actually endangers our lives.

The effects of these poor choices compromise every system that keeps us well, and the damage is not pretty. After years of a diet high in refined carbohydrates, arteries become narrow and clogged with plaque, raising the risk of cardiovascular disease and heart attack. We find ourselves on the unhealthy path to metabolic syndrome, type 2 diabetes, osteoarthritis, and cancer. Eating too much of the wrong foods and getting too little exercise allows fat to build up around our organs and beneath our skin. Smoking fills our lungs with toxins, damaging our health in myriad ways. Not getting enough sleep worsens our memories and disrupts an important hormone cycle that prevents us from overeating. And too much stress compromises our body's natural immune system, the very tool that would help us combat much of the other damage.

The Stress Reaction

The stress reaction is produced by your body's autonomic nervous system (ANS), which controls functions that happen more or less automatically in your body, like respiration, heart rate, and digestion. The sympathetic nervous system (SNS) and parasympathetic nervous system (PNS) are both parts of the ANS, and they act in opposition to one another. The SNS generally increases physiological arousal and creates the "fight-or-flight" response, while the PNS generally decreases physiological arousal and is responsible for calming your body down after a stressful incident.

In times of stress, the SNS stimulates the adrenal glands to increase the amount of noradrenaline, a neurotransmitter, they secrete into the bloodstream along with another, more powerful neurotransmitter, adrenaline. These neurotransmitters affect the entire body, and their effects last for hours. The adrenal glands also secrete cortisol, the primary stress hormone, which increases organ sensitivity to adrenaline and noradrenaline. These events take place through a complex series of interactions between the hypothalamus, pituitary gland, and adrenal glands, which together constitute the HPA axis.

Adrenaline:

• Increases your heart rate
• Elevates your blood pressure
• Increases energy supplies (glucose and fatty acids) in the bloodstream
• Increases blood flow to the liver and skeletal muscles while constricting smaller vessels

Cortisol:

• Increases sugars (glucose) in the bloodstream
• Enhances your brain's use of glucose
• Heightens your immune system
• Increases availability of tissue-repairing substances
• Suppresses the digestive system
• Inhibits growth processes
• Suppresses the reproductive system

The PNS is responsible for recuperation and allowing your body to return to a balanced state, known as homeostasis, after stress.

Chronic Stress

Originally the fight-or-flight response of the SNS protected us against threats from predators and other aggressors. It was designed as a temporary response to occasional threatening situations, and when the situation had been resolved the body's PNS took over, returning the body to homeostasis in what may be termed the "relaxation response."

But times have changed. Now, stressors may be anything from high-pressure jobs, to being stuck in traffic, to living on a tight budget. These sorts of stressors aren't temporary and infrequent: they're ongoing. We experience them day in, day out. If you are very frequently stressed, your body is subjected to a constant deluge of stress hormones and kept in a state of physiological arousal. You can end up becoming chronically stressed by the endless stream of stressors you face in the course of a day. This chronic stress can literally wear you out, and your body can become exhausted.

Chronically high levels of stress can:

• Lead to hypertension
• Increase levels of LDL ("bad") and decrease levels of HDL ("good") cholesterol
• Impair cognitive performance
• Suppress thyroid function
• Decrease muscle tissue
• Create blood sugar imbalances like hyperglycemia
• Decrease bone density
• Suppress the immune system
• Increase abdominal fat

In the long run, being chronically stressed can lead to heart disease, kidney disease, and stroke.

The Relaxation Response

The relaxation response of the PNS allows ANS functioning to return to normal. The body moves from a state of physiological arousal, including increased heart rate and blood pressure, decreased blood flow to the extremities, slowed digestive functioning, and increased levels of stress hormones, to a state of physiological relaxation. Your heart rate, blood pressure, blood flow, digestive functioning, and hormone levels return to their normal state.

Your fight-or-flight reaction occurs automatically and without any effort on your part. But under conditions of chronic stress, the relaxation response may never be activated. To undo the negative impact of ongoing stress, you need to consciously elicit the relaxation response.

Fortunately, there are many ways to bring the stress response under control. You can seek out support from family, friends, or professional counselors. Aerobic exercise, like running, cycling, and swimming, is usually an effective stress reducer. You might find that activities as spontaneous and unstructured as singing, gardening, playing with kids, or having sex are sufficient to put you into a relaxed state of being. Some people find that having a good cry relieves their stress. Or, you might find you need to use more structured approaches to destressing, such as meditation, deep breathing exercises, yoga, t'ai chi, self-hypnosis, and guided imagery.

Deep Breathing

Deep breathing is a popular, effective, and easy-to-do stress reliever that you can practice at home or at the office. Try the following: sit in a comfortable position with your feet flat on the floor. Relax your shoulders. Exhale slowly through your nose, counting to five. Tense your abdominal muscles to help empty your lungs. At the bottom of your exhalation, pause for two counts. Now inhale slowly while counting to five. Expand your belly as you breathe in. Pause for two counts at the top of your breath, close your eyes, and begin your exhale. Repeat 5-10 times.

Whatever method you choose, it should produce a feeling of calm and deep well-being in you. Once you experience that feeling, you'll probably find that you want to return to it again and again, making it easier to acquire the good habit of relaxation.

What exactly is stress? Stress is a challenge to your body or mind, termed a stressor, that elicits a physical response; a readiness to react. Describing the symptoms of the stress response is easy. Everyone recognizes at once the heart-pounding adrenaline surge they feel when a stressor has presented itself. Your body sets off alarms that tell you “Pay attention! Do something!”

The physical sensations you feel when stress strikes are rooted in your prehistoric ancestors' drive to survive. Early humans faced off with wild, carnivorous animals (and with other humans as well). To outrun or overcome these predators and competitors, and avoid becoming prey themselves, our ancestors developed a set of physical adaptations to focus all possible energy on survival. Stress hormones temporarily boost your strength, speed, and alertness—the qualities that could help you flee from a saber-toothed cat. Energy is sapped from your digestive organs, reproductive organs, and other systems that are not necessary for immediate survival. It's all focused on preparing you to run or take on your opponent in battle, the reaction we still call “fight or flight.”

These days, there are no saber-toothed cats. Instead, environmental factors and social or psychological challenges are standing in as the main stressors. Modern stressors, though, tend to be continual, rather than sporadic—for instance, you may have to drive through heavy traffic twice a day. But your body has not adapted to the new reality. Physiologically speaking, you react to an angry boss with the same physical sensations that your ancestors developed to react to life-or-death challenges. As a consequence, your body is constantly, and unnecessarily, flooded with stress hormones like cortisol. Sometimes, however, your stress response proves to be a positive thing. Mild stress, caused by having a deadline or answering a child’s cry, keeps you engaged and productive in your life. You can learn to manage stress by dealing with it in a positive way. So long as the stressors in your life do not overwhelm the system, you can learn to recognize your stress response and bounce back more efficiently over time.

The way we are programmed to react to stress is no match for the modern world. So many things trigger our stress response! When the stress response is rare, damage is minimal. But when our bodies are flooded with stress hormones repeatedly, damage is unavoidable.

Stress causes a cascade of hormones to be released. These stress hormones trigger many adverse physical reactions. When you’re under stress, your brain signals the release of the hormone cortisol from the adrenal glands that sit on top of your kidneys. Cortisol has far-reaching effects in your body, influencing your metabolism, immune system, memory, and more.

When cortisol levels are continually high because you’re chronically stressed, health problems start to arise. Consistently high cortisol levels may cause hypertension (high blood pressure), high blood glucose levels, and atherosclerosis. They can also affect brain function. It’s important to deal with stress-related medical conditions as soon as possible, because as time passes they become harder to treat. For instance, your kidneys are filled with millions of tiny, delicate blood vessels. Chronic hypertension can damage those blood vessels. Addressing hypertension early on may prevent damage to the kidneys and your chances of developing kidney disease.

Damage to the kidney’s blood vessels is just one example. The following sections will cover in greater detail what happens to your heart, blood vessels, brain, and even your weight when they are under great stress.

Stress creates an increased demand for oxygen throughout the body. In times of stress, your blood vessels are dilated (this means that they enlarge to let more blood through), you breathe more rapidly, and your body is ready to run—the “fight or flight” response. Your heart must work harder, beating faster to speed oxygen-rich blood to your extremities. The heart, as you know, is a muscle. All this hard work makes your heart larger, but in this case that isn’t a good thing. An enlarged heart is a weaker heart that doesn’t work as efficiently, so it can’t pump hard enough to deliver oxygenated blood to all of your extremities. Tissues may have too little oxygen to thrive or repair cells. The kidneys are one example of an organ in which lack of sufficient oxygenated blood can cause inefficient function and dangerous complications.

IMAGE: A comparison of a normal-sized (left image) and an enlarged heart (right image)

Stress can also contribute to irregularities in the electrical impulses that accompany each heartbeat. These complications create a greater risk of abnormal heart rhythms, heart failure, and heart attack in people with chronic stress.

As you’ve learned, your body responds to stress by producing the hormone cortisol. One of cortisol’s effects on the body is to raise blood glucose levels. This makes sense in the short term: It’s helpful to have quick energy available when an emergency arises. But chronic (long-term) stress creates chronically elevated glucose levels.

The cells that line blood vessels, known as endothelial cells, are very sensitive to glucose levels. When levels of blood glucose are very high, too much glucose ends up inside endothelial cells because these cells can’t limit their glucose uptake. The abnormally high glucose levels within the endothelial cells starts a whole chain of events that damages the cells in numerous ways and eventually kills them. And one thing is clear: Damage to the lining of the blood vessels creates a cascade of events that leads to cardiovascular disease.

One of the principle causes of cardiovascular disease is atherosclerosis, also known as hardening of the arteries. In atherosclerosis, lipid transporters (such as LDL-particles), calcium, and even our own protective white blood cells build up inside damaged blood vessel walls and form plaques. As plaques accumulate, they narrow blood vessel interiors and limit the flow of blood to cells and tissues, starving them of oxygen.

IMAGE: Fatty deposits build up inside arteries (left image) forming atherosclerotic plaques in the vessel wall (middle image). These plaque deposits can loosen and break off (right image).

Plaques may rupture and trigger blood clots. Blood clots can block blood flow if they stay in one place, or they may break off, travel through the vessels, and then become lodged in different places. If they lodge in the coronary arteries that feed the heart muscle, they can cause heart attacks. If the clot travels to the arteries that feed the brain, they may cause stroke.

Recent research suggests that stress takes a toll on the brain, too.

Part of the fight-or-flight reaction caused by stress affects your short-term recall. Stress hormones suppress activity in the prefrontal cortex part of your brain, which is thought to store short-term memories. The prefrontal cortex also plays a major role in concentration, inhibition, and rational thought. The social and intellectual brain tasks that might come to you automatically under normal conditions are also temporarily shelved when you are facing acute stress. Your powers of observation and focus are heightened, but calling up short-term memories is not high on the list of operations necessary for immediate survival.

Another part of your brain that handles memories, the hippocampus, is more active when you are under stress. When you are experiencing an intense, emotional episode, neurotransmitters signal the hippocampus to store it away in long-term memory. Back in prehistoric times, this memory task would have been essential to avoiding stress-provoking environmental factors in the future.

However, long-term exposure to high levels of cortisol causes neurons to shrink and interferes with their ability to communicate with other cells. In particular, the hippocampus has shown to be very vulnerable to chronic stress. Any cell damage that occurs in the hippocampus means that your memory and learning may suffer. Alarming physical damage to the hippocampus has been seen among survivors of extreme, life-threatening trauma. In two separate studies—one examining combat veterans, the other examining survivors of sexual abuse—victims' brains were scanned. The hippocampi of those who had experienced severe trauma were as much as 25% smaller than average.

The hippocampus is also part of the feedback mechanism that signals your body to halt cortisol production, allowing your system to recover from a stressful situation. A damaged hippocampus can cause cortisol levels to rise unchecked, creating a vicious cycle of destruction.

Researchers believe that chronic stress shifts the immune response by changing the “recipe” for the kinds of immune cells produced. Cytokines, substances secreted by immune system cells, have a range of roles in the immune system. In the presence of excess cortisol, some cytokines that provide immunity against infection are produced at very low levels. This allows for overproduction of another kind of cytokine that can stimulate allergic and autoimmune reactions, throwing the overall balance of immune cells out of line.

Acute stress, or brief episodes of stress that are resolved after a relatively short time and do not persist, are not associated with this change in immunity. It's the slow wear of chronic stress, which leaves overabundant cortisol to effect immune system changes, that causes the shift in immune cell production.

The taxing effect of stress on the immune system can leave your body more susceptible to everything from colds and flu to cancer. Stress has also been observed to exacerbate many chronic conditions:

Asthma

Being stressed alters your respiration rate and is thought to amplify the inflammatory response in the lungs. This is why stress is a common trigger of asthma attacks in those who are vulnerable.

Arthritis

People with moderate-to-severe arthritis often experience psychological stress due to pain and the demands of managing the disease. The increased muscle tension that is part of the stress response can intensify the usual discomfort of arthritis inflammation and make arthritis sufferers feel even worse.

Acne

Stress doesn't cause acne, but high stress can trigger flare-ups in those who already suffer from the skin ailment. A Stanford University study in 2003 found that college students had many more acne flare-ups during the stress-filled weeks of final exams, compared to periods without testing.

There are several ways in which stress can contribute to weight gain. The main culprit, again, is cortisol!

One benefit of cortisol is that it provides your body with energy when it needs it, such as in high-stress, life or death situations. This allows you to react appropriately by fighting or running away at top speed. It turns out that under cortisol’s influence, you are also less sensitive to leptin, the hormone that makes you feel full. This causes you to eat more than you normally might. In the past, this would have made sense, encouraging you to refuel your energy once the threat was gone.

The problem in these times is that this sequence of events takes place whether the threat is real or psychological. Since most of today’s stressors don’t require fleeing or fighting, you generally don’t need all of the extra calories your body makes available, or the extra calories it causes you to crave. Many people now exist in a state of constant stress, operating with elevated cortisol levels over long periods of time. This has led to an unnecessary craving and overconsumption of food, particularly carbohydrates. The “fuel” our muscles want during “fight or flight” is sugar—one reason you crave carbohydrates when you’re stressed. The extra glucose flooding your blood from the effects of cortisol and from an increased consumption of refined carbohydrates also leads to an increase of insulin in the blood. Insulin in the blood, as you know, leads to increased fat storage in your fat cells.

And it gets worse. All this fat is stored primarily as visceral fat, the fat that lies deep within your belly—close to many of your vital organs. Scientists have discovered that fat cells have special stress-hormone receptors for cortisol, but there also seem to be more of these cortisol receptors on the fat cells in the belly than anywhere else in the body! What’s more, visceral fat has a greater blood supply than other types of fat, so more cortisol is delivered there, rather than to other areas of fat in your body.

All of this adds up to more and more storage of visceral fat. This is a real hazard to your health, because visceral fat is linked with greater health risks, such as type 2 diabetes and heart disease, than fat stored in other areas of the body.

You might be slightly stressed just reading about all the damaging effects that chronic stress does to your body. Don’t worry! The best thing that you can do for yourself is to identify symptoms of stress and tackle them before they get too out of hand. The following sections will help you identify how stressed you are and also how you can tackle that stress.

Feelings of anxiety, sadness, and general malaise may be caused by stress, even though they may not seem to be directly connected. Everyone feels negative emotions sometimes. If you’ve had many challenges at work or home and start experiencing negative feelings more frequently, that could be a red flag that stress is altering your mood.

The same goes for any changes in behavior that come on suddenly after you’ve been stressed out. Watch for changes from your usual habits or routine. They could indicate that your body is trying to combat the effects of stress, and you should pay attention to those warning signs. For instance, if your use of tobacco, alcohol, or other drugs increases, or you feel like avoiding social situations, be careful about chalking it up to a temporary phase. If you can identify the root cause as stress, then you can take steps to manage it better.

Take action to curb chronic stress in your life. Identify pressure situations and see if you can change them. If traffic jams stress you out, take a longer, less congested route, or listen to recorded books during your drive. If you’re a caregiver for children or ailing elders, get help so that you can take a break and de-stress. Not all stressors can be removed from your life, but there are many methods for coping with stress that will improve your health and happiness.

Get a Good Night’s Sleep

Getting enough deep sleep keeps your stress hormones in balance. If you miss a few hours of sleep one night, your natural stress response is affected, and your cortisol levels are higher than usual the next day. In one study, people deprived of sleep for 32 hours had a 45% increase in cortisol! Sleep has also been shown to help people rebound from stressful experiences.

If you are over 18, aim to get at least 7 hours of sleep per night— 8 or 9 hours, if you don't feel alert and energized when you wake up. If you have trouble sleeping, develop a nightly routine of easing into sleep with soothing activities. Try to stick to a regular bedtime and wake-up time every day.

Have an Active Social Life

Social connections are crucial for alleviating stress. Whether you spend time with your friends exercising, sharing a meal, or swapping stories about your stressful day, you are relieving stress. Researchers at the Gallup polling organization found that people who said that their best friend worked with them were seven times more likely to be top performers at work. Their recommendation for maximizing stress relief: Aim to spend at least 6 hours a day connecting with friends, family, and colleagues. That may seem like a lot, but it includes connecting at work, at home, on the phone, by email, or any other form of communication.

Exercise Regularly

In one research study, a group of subjects over 50 years of age who had been diagnosed with major depressive disorder were split into three groups. One group started an aerobic exercise training program. A second took a leading antidepressant medication. The third group combined the two interventions—some exercise and the antidepressant. After 16 weeks, all three groups showed improvement in their depression symptoms. The group taking the drug had more immediate improvement, but by the end of the research period it was clear that the exercise-only group had improved just as much as the other two. Exercise may be the best antistress prescription of all!

Own a Pet

We’re not necessarily saying that you should go out and get a pet, but if you already have a family pet, or are in the market to get one, you might be pleased to hear that owning a dog might be associated with decreased stress and cardiovascular disease. However, this only seems to work if you are the one who walks your dog and have formed a close bond with your pet. A recent statement from the American Heart Association said that owning a pet, in particular a dog, could be associated with reduced stress and heart risk. Other studies have found that owning a cat is associated with reduced stress as well.

Meditate Daily

Studies have shown that daily meditation helps to alleviate stress and can measurably lower cortisol levels. Meditation practice is one of the key stress interventions being studied by medical researchers, and it has proven to be very effective. There is more than one way to practice meditation, and you should find the approach that works best for you. Some practices use a focusing word or image to help a practitioner clear other thoughts from the mind. What every practice has in common is devotion of a certain amount of time to directing attention inward and quieting the mind.

Embracing more positive emotions is another key to handling stress. People who are happy have been found, in some studies, to have less pain, better cardiovascular health, and better memory. The next section reveals the massive health benefits of being happy and joyful.

Have you ever wondered why people who are stressed often seem to have a haggard look about them? A pioneering study from 2004 suggests that the reason is because stress can actually accelerate the cell biology of aging.

Stress, it seems, can shorten telomeres, which are segments of DNA that protect the ends of chromosomes. Shortened telomeres can inhibit or block cell division, which includes growth and proliferation of new cells, thereby leading to more rapid aging (Sapolsky, 2004). In the study, researchers compared telomere lengths in the white blood cells in mothers of chronically ill children to those of mothers of healthy children (Epel et al., 2004). Mothers of chronically ill children would be expected to experience more stress than would mothers of healthy children. The longer a mother had spent caring for her ill child, the shorter her telomeres (the correlation between years of caregiving and telomere length was r = -.40). In addition, higher levels of perceived stress were negatively correlated with telomere size (r = -.31). These researchers also found that the average telomere length of the most stressed mothers, compared to the least stressed, was similar to what you would find in people who were 9–17 years older than they were on average.

Numerous other studies since have continued to find associations between stress and eroded telomeres (Blackburn & Epel, 2012). Some studies have even demonstrated that stress can begin to erode telomeres in childhood and perhaps even before children are born. For example, childhood exposure to violence (e.g., maternal domestic violence, bullying victimization, and physical maltreatment) was found in one study to accelerate telomere erosion from ages 5 to 10 (Shalev et al., 2013). Another study reported that young adults whose mothers had experienced severe stress during their pregnancy had shorter telomeres than did those whose mothers had stress-free and uneventful pregnancies (Entringer et al., 2011). Further, the corrosive effects of childhood stress on telomeres can extend into young adulthood. In an investigation of over 4,000 U.K. women ages 41–80, adverse experiences during childhood (e.g., physical abuse, being sent away from home, and parent divorce) were associated with shortened telomere length (Surtees et al., 2010), and telomere size decreased as the amount of experienced adversity increased (Figure).

Efforts to dissect the precise cellular and physiological mechanisms linking short telomeres to stress and disease are currently underway. For the time being, telomeres provide us with yet another reminder that stress, especially during early life, can be just as harmful to our health as smoking or fast food (Blackburn & Epel, 2012).