Chronic pain is a serious health problem that affects millions of people around the world. Unlike the sharp pain you feel after an injury that fades as the body heals, chronic pain can last for months or even years.
It can interfere with sleep, work, relationships, and everyday life. Doctors have long noticed that women report long-lasting pain more often than men, but the reasons behind this difference have not been clear.
Some people believed it was due to emotional factors or differences in how pain is described. However, new research suggests that the answer may lie deep inside the immune system.
Scientists at Michigan State University have discovered an important biological difference that may explain why chronic pain tends to last longer in women. Their study found that certain immune cells, called monocytes, play a key role in turning pain off. Monocytes are a type of white blood cell that help the body fight infection and repair damage.
They travel through the bloodstream and move into tissues when needed. For many years, scientists believed these cells mainly acted as helpers in the immune system, but this new research shows they also communicate with the nervous system.
The researchers discovered that a special group of monocytes releases a calming signal that tells pain-sensing nerves to stop sending pain messages.
This signal comes from a molecule called interleukin-10, or IL-10, which reduces inflammation and helps the body return to normal after injury. In men, these IL-10-producing monocytes are more active, partly because of higher levels of male sex hormones such as testosterone. As a result, men may recover from pain faster.
In women, however, these cells were less active, which meant the pain signals continued for a longer time. The scientists observed that female mice and women patients both showed delayed recovery from pain. This finding suggests that the difference is not about tolerance or personality, but about how the immune system responds after injury.
Pain happens when special nerve cells in the body detect damage or danger and send signals to the brain. Normally, these signals stop once healing begins. In chronic pain, however, the alarm system stays switched on even when there is no clear injury.
Everyday sensations such as touch or movement can become painful. This condition can develop after accidents, surgery, or illnesses, and sometimes it appears without a clear cause.
The research team spent several years studying how pain is controlled in the body. They first noticed that male subjects had higher levels of IL-10, the molecule that quiets pain.
After repeating the tests and confirming the pattern, they used advanced laboratory methods to identify the exact immune cells responsible. When the researchers blocked male hormones in animal models, the pain-relieving cells became less active, further proving the connection between hormones and immune response.
To make sure their results were reliable, the scientists carried out multiple experiments using different methods. They also collaborated with another research group studying people who had been injured in car accidents.
That group found the same pattern: men had more active pain-calming immune cells and recovered more quickly, while women were more likely to develop long-lasting pain.
This discovery changes the way scientists think about chronic pain. Instead of focusing only on how pain begins, researchers are now looking at why pain does not stop.
The immune system appears to play an active role in shutting down pain signals, not just fighting infection. Understanding this process could lead to new treatments that help the body heal naturally rather than simply blocking pain with strong medications.
These findings are especially important because many current pain treatments rely on opioids, which can cause addiction and serious side effects.
If scientists can learn how to boost the activity of these pain-resolving immune cells, it may be possible to develop safer, non-opioid therapies. Such treatments could help people recover faster and prevent chronic pain from becoming permanent.
The study also highlights the importance of taking women’s pain seriously. For many years, women’s reports of pain were sometimes dismissed or misunderstood.
This research shows that biological differences in the immune system can affect how pain is experienced and resolved. Recognizing these differences may lead to more personalized treatments that consider sex-specific factors.
In reviewing the findings, the study provides strong evidence that chronic pain is influenced by immune and hormonal factors, not just by injury or psychological perception. The use of both animal models and human data strengthens the conclusions.
However, more research is needed to understand how these immune cells can be safely targeted in treatments and whether other factors, such as age or health conditions, also influence pain recovery.
While new therapies may still be many years away, this discovery opens an important path toward better pain management and fairer care for both men and women.
If you care about pain, please read studies about how to manage gout with a low-purine diet, and a guide to eating right for arthritis.
For more health information, please see recent studies about the link between processed foods and chronic diseases, and avoid these 8 foods to ease arthritis pain.
The study is published in Science Immunology.
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