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A new study has uncovered why some individuals remain hypersensitive to stress and pain long after an injury has healed—and the answer lies deep within the brain’s intricate circuitry. Research from the University of Toronto Mississauga reveals that the nervous system can remain “primed” for danger due to changes triggered by past trauma, potentially setting the stage for chronic pain and anxiety disorders.
Injury Leaves an Invisible Mark
This groundbreaking research, published in Current Biology, found that mice who had experienced a previous injury displayed more intense reactions to stress and fear, such as the scent of a predator, compared to their uninjured peers. Notably, these mice developed long-lasting pain in both hind paws, even on the side that was never injured. Alarmingly, these heightened responses persisted for more than six months—long after any physical signs of injury had disappeared.
“Our brains are wired to protect us—especially from threatening situations,” explained Dr. Loren Martin, the study’s senior author. “But sometimes that protective system stays switched on—leaving us overly sensitive to stress or pain, even when the threat is long gone.”
The Science Behind Long-Lasting Fear and Pain
First author Jennet Baumbach discovered that the body’s stress hormone, corticosterone, collaborates with a protein known as TRPA1—familiarly dubbed the “wasabi” receptor for the burning sensation it mediates. This partnership appears to set off a biological feedback loop, heightening the brain’s preparedness for future threats and intensifying both fear and pain responses even in the absence of new injury.
Interestingly, while both the TRPA1 receptor and corticosterone were necessary for the mice’s exaggerated fear response, only ongoing stress hormone signaling was required to maintain their chronic pain—hinting at separate mechanisms for these two symptoms. Blocking either the stress hormone or the TRPA1 receptor reversed these effects, offering promising new targets for therapies against chronic pain, PTSD, and related conditions.
“We’re dissecting the brain and central circuits that control these behaviors,” said Dr. Martin. “By understanding how trauma rewires the nervous system, we can begin to target the mechanisms that keep fear and pain locked in place.”
Implications for Treatment
The findings shed new light on why early injuries or traumatic experiences can shape the body’s response to stress and pain far into the future. Developing treatments that interrupt these feedback loops may help millions living with chronic pain and anxiety.
Disclaimer: This article is for informational purposes only and does not constitute medical advice. If you are experiencing chronic pain or mental health concerns, please consult a healthcare professional for guidance and treatment recommendations.
