What Is Psychoneuroimmunology?

Medically Reviewed by Melinda Ratini, MS, DO on June 08, 2021
4 min read

If you've ever gotten sick during a time when you were under a lot of stress, it probably won't surprise you to learn that your immune system is affected by your stress level.

Psychoneuroimmunology is the study of how your immune system and your central nervous system interact. Psychological stress makes you more susceptible to everything from the common cold to flare-ups of autoimmune diseases.

Your body's first defense against illness or injury is called the "sickness" response because it's what makes you feel sick. It's what gives you a fever, reduces your appetite, and makes you feel anxious. It also releases stress hormones such as cortisol. The sickness response is your body's attempt to save energy for fighting an infection.

When your immune cells arrive on the scene of an infection, they release cytokines. Your vagus nerve, which runs from your abdomen to your head, has receptors for parts of these cytokines. When these receptors are activated, they send a signal to your brain to make its own cytokines. This causes your brain to send a response back to your immune system, which further activates your immune response.

This connection between your brain and your immune system runs both ways. It doesn't work without the vagus nerve. If your brain doesn't get the message from the vagus nerve, it won't trigger the sickness response. The reverse is true as well. 

In early studies where cytokines were placed in the brains of animals, the sickness response was triggered even when there was no infection.

Stress may cause your body to have the same sickness response as infection or illness. The only difference is that it originates in the brain instead of being triggered by your immune cells. Your brain produces cytokines in response to stress exactly like it does in response to a message from your vagus nerve.

Even though stress triggers your body's immune response, it may lessen your ability to fight actual infections. Chronic stress causes your body to produce cytokines over a long period of time. Cytokines are inflammatory. Chronic inflammation increases your risk of developing:

Studies have shown that even short-term stress affects your immune response. But the real danger comes from chronic stress that builds up over time. Chronic stress suppresses your immune system. Studies have linked chronic stress to the following diseases:

Asthma. Psychological stressors can trigger asthma attacks. People with asthma who were exposed to harmless substances that they thought would cause an asthma attack were likely to suffer severe reactions. Another study showed that people who were under stress showed a stronger allergic response on skin allergy tests than people who weren't.

Heart disease. People who have had a heart attack are more likely to report stressful events in their lives, including:

  • Stress at work
  • Stress at home
  • Major life changes
  • Financial stress

A study of men with heart disease found that those who experienced 3 or more major stressful events were twice as likely to die from heart disease.

Cancer. Researchers are still trying to figure out if chronic stress helps to cause cancer growth. It may allow cancer to spread and grow. Part of the way your body fights cancer is through anoikis, which kills diseased cells and stops them from spreading. Stress hormones suppress this process.

Stress has a lot of negative effects on your health, so it's important to learn to manage it. You can't get rid of all of the stress in your life, but you can follow the 4 A's to help you reduce your chronic stress. These A’s include avoid, alter, accept, and adapt.

Avoid. Learn to say no to events and people that cause you stress. Don't take on extra tasks that overload your schedule. If your morning commute stresses you out, try to find a more peaceful path to work.

Alter. For situations you can't avoid, try to do what you can to change them. Respectfully ask people to change their behavior if it's negatively affecting you. Set firm limits and stick to them. Learn to communicate your frustrations using "I" statements. 

Accept. There are times when there will be nothing you can do to avoid or change a situation. When this happens, you may need to talk with a therapist. Other acceptance strategies include learning from your mistakes, trying to forgive, and practicing positive self-talk. 

Adapt. Sometimes you need to change your standards or expectations to adapt to stressful situations. You may need to lower your standards on some things for a short time. Look at the big picture for perspective. Think ahead 5 years and ask yourself if what you're worrying about will matter in 5 years.