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When we have an extremely stressful experience, such as losing a loved one or being constantly bullied by a classmate, our body can react in different ways. Sometimes we overcome the psychological stress and come out stronger than before. Other times, we fall victim to the stress. These experiences build mental “toughness,” also called psychological resilience, which plays an important role in whether we develop mental health disorders, such as depression or anxiety, due to stress. Psychological resilience may sound like something that happens in our head, but it turns out that the immune system is involved in the process.

A group of scientists from the National Institutes of Health reported that the cells of the immune system can change during stress to protect the body from the harmful effects of psychological stress. They made this discovery by stressing out special mice called Rag2-/- mice that do not have immune cells. When stressed, the Rag2-/- mice became anxious and developed depression-like symptoms. When the researchers injected the Rag2-/- mice with the immune cells of stressed normal mice, the Rag2-/- mice became less anxious. This exciting finding tells us that stressed-out immune cells are important in increasing our mental toughness and helping us overcome stressful experiences.

Scientists do not yet understand exactly how stressed immune cells protect the body from psychological stress, but it is very promising that immune cells can one day be used to treat mental health disease and health problems, such as cardiovascular diseases, that are caused by psychological stress.

Dao H. Ho, PhD, is a biomedical research physiologist at Tripler Army Medical Center.

The views expressed in this blog post are those of the author and do not reflect the official policy or position of the U.S. Department of the Army, U.S. Department of Defense or the U.S. government.