Chronic pain—defined as pain that lasts for three months or more—is not only physically exhausting but also closely connected to mental health issues like depression.
A growing body of research shows that people with chronic pain are up to four times more likely to experience depression. Now, new research from Yale University adds an important piece to this puzzle: inflammation in the body may be a key reason why pain and depression are so closely linked.
The study, published in Science Advances, examined health data from the UK Biobank, one of the world’s largest medical databases. It includes information from over 400,000 people collected over 14 years.
Participants reported where in the body they felt pain (such as in the back, neck, head, or joints), how long it lasted, and whether it interfered with their daily lives. They also answered questions about their mental health and whether they had been diagnosed with depression.
The researchers found that people who experienced pain in more than one part of the body were more likely to suffer from depression. In fact, the risk of depression increased as the number of painful body sites increased. The link was stronger for those with chronic pain than for those whose pain lasted only a short time.
But the study went even further. Blood samples from participants were analyzed for signs of inflammation—specifically, for proteins and cells that the body produces when it is fighting off infection or injury. One marker, called C-reactive protein (CRP), stood out. This protein is made in the liver and increases in the bloodstream when the body is inflamed.
The researchers found that people with higher levels of CRP were more likely to experience both pain and depression. This suggests that inflammation may be a shared biological cause of both conditions.
“This gives us some preliminary evidence about the inflammatory mechanisms underlying the association between pain and depression,” said Dr. Rongtao Jiang, the study’s first author and a postdoctoral researcher at Yale School of Medicine.
According to senior author Dr. Dustin Scheinost, an associate professor at Yale, the findings highlight how deeply connected our physical and mental health are. “Pain isn’t only physical,” he said. “Our study adds to the evidence that physical conditions can have mental health consequences.”
This research challenges the old view that treats mental health as completely separate from other areas of health, such as the heart, liver, or immune system. Instead, it supports the idea of a brain-body connection, where inflammation in one part of the body can affect how the brain works, and vice versa.
This insight may lead to new treatment strategies. If inflammation plays a central role in both chronic pain and depression, then targeting inflammation might help ease both problems at once.
Currently, depression is mostly treated with therapy and medications that affect brain chemicals. But for people whose depression is linked to physical pain, anti-inflammatory approaches may one day offer relief.
The study also found that even short-term (acute) pain was connected to depression, although not as strongly as chronic pain. This reinforces the idea that any kind of ongoing discomfort—especially in multiple places—can take a toll on mental well-being.
While these findings are promising, the researchers noted that most of the people in the study were of European ancestry. Future research will need to look at whether these results hold true in more diverse populations.
The team is also planning to explore the connection between chronic pain and opioid use disorder, a serious problem that often develops when people try to manage long-term pain.
In summary, this study helps explain why so many people with chronic pain also struggle with depression. It shows that inflammation—measured through markers like CRP—might be the common link. These insights could eventually lead to better, more personalized treatments for millions of people living with chronic pain and its emotional toll.
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 research findings can be found in Science Advances.
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