The Effects of Stress on the Body, From Your Brain to Your Stomach

Stress is what happens when you're introduced to a challenge or demand in life—it results in physical or emotional tension, according to the US National Library of Medicine's MedlinePlus resource. 

It's a normal feeling that has evolved over a millennium to protect you from danger. Also known as the flight-or-fight response, it gets the body ready for action. So if you're in danger, the brain's hypothalamus sends triggers—both chemical and along the nerves—to the adrenals, which are glands that sit on top of each kidney like a hat perched on a head.

The adrenals then churn out hormones, such as cortisol, which raise blood pressure and blood sugar (among other things). This is dandy if you need to outrun a hungry lion, less so if the perceived threat is a looming layoff. 

Despite the fact that it happens to everyone, stress can still be harmful to health if occurs over a long period of time. Here are the ways stress can affect your health—and what you can do about it. 

Studies have linked cortisol, a hormone released during times of stress, to cravings for sugar, fat, or both, according to Harvard Health Publishing.

Scientists believe the hormone binds to receptors in the brain that control food intake. And if you already naturally carry more weight, you may be even more susceptible—possibly due to already high insulin levels. 

The key is to know your triggers, and be ready when stress is likely to hit. That means, stock up on healthy snacks if you tend to hit the vending machine at work, or make sure you don't unhealthy treats on hand for those times when an attack of emotional eating is likely.

"You can clearly correlate stress to weight gain," Philip Hagen, MD, an assistant professor of medicine at the Mayo Clinic, tells Health.

Part of that link is due to poor eating during stress, but the stress hormone cortisol may also increase the amount of fat tissue your body hangs onto and enlarge the size of fat cells. Higher levels of cortisol have been linked to more deep-abdominal fat—yes, belly fat.

Exercise can help control stress and help keep belly fat under control, if that's something you're concerned about.

The exact relationship between stress and heart attack is still unclear, but evidence is mounting that there is one. One study of 200,000 employees in Europe found that people who have stressful jobs and little decision-making power at work are 23% more likely to have a first heart attack than people with less job-related stress.

According to the American Heart Association, stress can also affect other behaviors and factors that increase heart disease risk, like smoking, physical inactivity, and overeating. 

The best thing to do is lead a heart-healthy lifestyle and focus on reducing stress in your life, like taking time off of work when you need it, or practicing mindfulness and meditation.

Stress can cause hyperarousal, a biological state in which people just don't feel sleepy. And insomnia itself—a sleep disorder in which a person has persistent problems falling and staying asleep—is commonly derived from stress.

While major stressful events can cause insomnia that passes once the stress is over, long-term exposure to chronic stress can continue to disrupt sleep and contribute to sleep disorders, like sleep apnea, according to the Sleep Foundation. 

What to do? Focus on sleep hygiene (making your surroundings conducive to a good night's rest) and try yoga or another stress-busting activity during the day.

"Fight or flight" chemicals like adrenaline (epinephrine) and cortisol can cause vascular changes that leave you with a tension headache or migraine, either during the stress or in the "let-down" period afterwards.

Tension headaches, per MedlinePlus, are the most common type of headache. They typically feel like a "band is squeezing the head," and occur in the head, scalp, or neck area. 

Because stress also makes your muscles tense, it can make an already bad headache even worse. Beyond treating the headache itself, focus on headache-proofing your home, diet, and lifestyle in general.

The link between memory and sleep is still not totally clear, but researchers believe that the quantity and quality of sleep people get can have an impact on learning and memory, according to the Division of Sleep Medicine at Harvard Medical School. 

The exact mechanism isn't fully understood, but there are some theories: One is that too much of the stress hormone cortisol can interfere with the brain's ability to form new memories.

During acute stress, the hormone also interferes with neurotransmitters, the chemicals that brain cells use to communicate with each other. That can make it hard to think straight or retrieve memories.

While it's tough to limit stress in our hectic lives, some experts recommend trying meditation, among other solutions.

There are a few key ways that stress may affect your hair and lead to hair loss, according to the University of Pittsburgh Medical Center: Telogen effluvium and trichotillomania.

Telogen effluvium is a common cause of temporary hair loss, per UPMC. That's because enough stress can push your hair follicles into a prolonged resting phase, meaning they won't produce new hair strands as quickly or as often as usual in periods of high stress. 

Stress and anxiety can also contribute to a disorder medically known as trichotillomania, in which people have a hard-to-resist urge to pull out the hair from their own scalp.

The normal stresses of everyday life are unlikely to affect a pregnancy, but severe stress, like losing a job or going through a divorce, can increase the chances of premature labor, according to the March of Dimes. Stress may also increase the risk of your baby having a low birthweight. 

Prenatal yoga and other stress-reduction techniques can help, so talk to your doctor if you're severely stressed and pregnant.

Stress is known to raise blood sugar, and if you already have type 2 diabetes you may find that your blood sugar is higher when you are under stress.

Changing what you eat, exercising more, or adjusting medication can help to keep it under control.

Heartburn, stomach cramping, and diarrhea can all be caused by or worsened by stress.

In particular, irritable bowel syndrome, or IBS, which is characterized by pain and bouts of constipation and diarrhea is thought to be fueled in part by stress.

One thing to keep in mind though: Stomach ulcers, once thought to be caused by stress, are triggered by H. pylori bacteria, which can be treated with antibiotics.

A stressful situation can raise your blood pressure temporarily by constricting your blood vessels and speeding up your heart rate, but these effects disappear when the stress has passed.

It's not yet clear whether chronic stress can cause more permanent changes in your blood pressure, but techniques like mindfulness and meditation may help, according to Dr. Hagen. In addition, there are many natural ways to reduce blood pressure, including diet and exercise.

Most acne sufferers already suspect this is true, and they seem to be right: Stress can give you zits. Research suggests that students with acne are more prone to outbreaks during exams compared to less stressful time periods. An increase of male hormones known as androgens could be a culprit, particularly in women.

Stress can also trigger psoriasis to appear for the first time or make an existing case more severe. Many doctors are starting to incorporate stress-management techniques such as biofeedback and meditation into their treatment programs for the skin disease.

Stress can set off an acute attack of back pain as well as contribute to ongoing chronic pain, probably for the simple reason that the "fight or flight" response involves tensing your muscles so that you're ready to spring into action.

One recent study in Europe found that people who are prone to anxiety and negative thinking are more likely to develop back pain, while a U.S. study tied anger and mental distress to ongoing back pain.

Here's another reason for guys to reduce their stress levels: According to a 2012 study published in the journal Nature Communications, researchers found that women were less attracted to men with high levels of the stress hormone cortisol, compared to men with lower levels. 

Researchers believe this may be because low levels of stress hormones suggest strength and health, which are desirable traits to be passed on to offspring.

Though research is still being conducted, there is evidence that stress may be a risk factor for stroke—particularly job-related stress, according to the Cleveland Clinic. 

"Sometimes stress can cause inflammation, hypertension, or other vascular conditions," Irene Katzan, MD, a neurologist at the Cleveland Clinic previously told the agency. This, then, can lead to stroke or heart attack, she said. 

Research published in the journal Neurology found the same connection. According to a meta-analysis in 2014, researchers found that having a high stress job (service industry workers, as well as doctors, teachers, and engineers) may be linked to a higher risk of stroke. 

Traumatic events and chronic stress can both shorten telomeres, the protective caps on the ends of cell chromosomes, causing your cells to age faster, according to Harvard Health Publishing. 

The good news? Exercising vigorously three times a week may be enough to counteract the effect.

People exposed to common cold viruses are less likely to fight off the germs successfully if they have ongoing psychological stress in their lives.

Researchers believe stressed people's immune cells may be less sensitive to a hormone that turns off inflammation, which could offer a clue to why stress can be correlated with more serious diseases as well.

According to the Asthma and Allergy Foundation of America, strong emotions (think: stress and depression) can actually trigger asthma. 

Researchers aren't sure why, but one theory is that stress may amplify the immune response to asthma triggers such as pollen, animal dander, or dust.

Another has to do with your breath: some experts believe that, when you experience strong emotions, your breathing changes slightly, possibly leading to asthma symptoms. 

Employees ranging from military personnel to bankers can experience reduced productivity as a result of stress, as well as less satisfaction at work and symptoms of depression. One solution is to ask your employer to offer stress-management training, which can address company-wide stressors like weak communication channels as well as focusing on stress busters for individuals.

"Stress clearly has an effect on productivity, and the costs of that for employers can be very high," Dr. Hagen points out.

Although it's not all that common, doctors at the John Hopkins Hospital have found that some people who are especially sensitive to stress can experience seizure-like symptoms, such as far-off staring and convulsions.

Up to one-third of people treated for seizures at the hospital didn't respond to standard anti-seizure medication and doctors concluded that they had stress-induced symptoms.

Known as conversion disorder, some people can subconsciously express emotional trauma as physical symptoms, they say.

According to the Mayo Clinic, your state of mind affects your sexual desire—that means stress, among other things, can actually reduce your sex drive. 

Sexual dysfunction can have medical causes, so it's important to talk to a doctor, but reducing and managing stress can often turn things around in the bedroom.