Medically Reviewed by Smitha Bhandari, MD on March 05, 2021
When something scares you suddenly, like a loud noise, it triggers stress hormones (adrenaline, noradrenaline, cortisol) that make your heart beat faster and harder. You may feel like it's beating unevenly (heart palpitations). Over time, if it happens too much, you're more likely to have high blood pressure, heart disease, hardened arteries, high cholesterol, stroke, and heart attack.
Along with a pounding heart, you might start breathing more quickly when you're scared or anxious, or feel like you can't get enough air. Some people breathe so fast that they get light-headed or pass out. It can be serious if you already have breathing problems because of asthma, lung disease, chronic obstructive pulmonary disease (COPD), and other conditions.
Fight or Flight Response
It's a set of symptoms you get when you react to something scary. Your fright triggers the release of certain hormones that send signals through your brain, spinal cord, and nerves. Blood and fuel (glucose) floods to your arms and legs to prepare to meet the threat with one of two options: fight or run away. Your pulse and breathing speed up. You also might get sweaty and shaky.
Your body gets ready to protect itself when you're anxious. If you're really startled, your muscles tense all at once. They usually relax once the stress passes, but if it happens a lot or if you feel worried all the time, your tight shoulder and neck muscles can lead to headaches, including migraines. Relaxation techniques like deep breathing and yoga may help.
High Blood Sugar
Stress hormones can give you a burst of this instant fuel when you're scared or anxious. It's helpful if you need to run from danger or fight it. Normally your body gathers up and stores the extra sugar. But high or constant anxiety could keep your blood sugar too high for too long. This can lead to diabetes as well as heart disease, stroke, and kidney disease.
Worry can keep you up at night. "Did I pay the power bill?" "Did I forget to feed the dog?" Poor sleep can ramp up anxiety even more, especially if you have to work the next day. A to-do list might lessen anxiety by breaking down problems to solve. And good sleep habits could help. Try to have regular sleep and wake times. Go to bed in a dark, cool bedroom. Also do a gradual slowdown at night to ease into bedtime.
Problems Fighting Off Germs
Your body may not beat back infections so well when you worry. Even just thinking about something that made you angry or sad can lessen the response of your immune system -- the body's defense against germs -- in as little as 30 minutes. Anxiety that stretches over days, months, or years can take an even bigger toll on the immune system, making it harder for you to fight the flu, herpes, shingles, and other viruses.
Stress and anxiety can make you feel like you have knots in your belly. Some people feel nauseated and even vomit. If this happens all the time, you can develop digestive problems like irritable bowel syndrome (IBS) or sores in your stomach lining called ulcers. Talk to your doctor if you have serious belly pain or vomit when you're anxious.
Anxiety can make you constipated. Doctors aren't sure exactly why, but it may be that being anxious changes the way you use the muscles that control how you poop. It can also give you diarrhea because it changes the way your body absorbs certain nutrients. Your gut may be especially sensitive to stress if you already have IBS or another digestive issue. Your doctor might be able to help you manage anxiety triggers in your life.
Part of the problem is that anxiety can sometimes make you eat more. It also may lead you to seek foods with lots of fat and sugar, which have more calories. And these foods seem to "work" in the sense that they improve anxiety symptoms, which makes you crave them even more. Over time, too much anxiety can mess up your body's stress response and cause you to put on some unwanted pounds.
Men's Sexual Problems
At first, stress can trigger your fight-or-flight system, which makes the hormone testosterone. That can make you feel more frisky. But another stress hormone, cortisol, can have the opposite effect. Over the long term, worry can actually decrease testosterone, change or lessen your sperm, and slow or stop your body's normal response when you want to have sex.
Women's Sexual Problems
Worry can tire you out and distract you, so you're less interested in sex. The cortisol stress hormone may also lessen desire. High levels of stress can affect your cycle. It can cause missed or uneven periods or make them longer or more painful. It may worsen cramping, bloating, and mood swings in the week before your period, sometimes called premenstrual syndrome (PMS). Anxiety can also make it harder to get pregnant.