Early life adversity primes the body for persistent physical pain, new research suggests

New research suggests that difficult experiences in childhood may prime the nervous system for chronic pain later in life. A study involving nearly 2,500 trauma survivors found that those with a history of abuse or bullying were more likely to suffer from persistent physical pain following a car crash or similar event in adulthood. The researchers validated these findings by observing similar patterns in laboratory rats. These results, published in the journal Pain, provide evidence that early life adversity is a biological vulnerability factor for poor recovery from injury.

Most people experience a traumatic event at some point in their lives. While the majority of individuals recover physically and emotionally, a subset develops chronic post-traumatic musculoskeletal pain. This condition is characterized by persistent soreness and discomfort that often continues long after physical injuries have healed. Medical providers have struggled to identify which patients are most at risk for this outcome.

The inability to predict who will develop chronic pain hinders the development of preventive treatments. Previous research has established that early life adversity can harm long-term mental health. Lauren A. McKibben, a researcher at the University of North Carolina at Chapel Hill, and her colleagues hypothesized that these early experiences might also affect physical pain processing. They sought to determine if childhood stress alters the body in a way that makes it harder to recover from physical trauma decades later.

To investigate this connection, the research team utilized data from a large nationwide project called the AURORA study. This project enrolled adults who sought care in emergency departments across the United States following a traumatic incident. The majority of these incidents involved motor vehicle collisions. The study design allowed researchers to track the participants’ recovery in real-time.

Two weeks after their emergency room visit, the participants completed surveys about their history. They answered questions from the Childhood Trauma Questionnaire regarding physical, emotional, and sexual abuse, as well as neglect. The researchers also included specific questions about whether the participants had been bullied by peers during their youth.

Over the following eight weeks, the patients reported their pain levels through digital surveys on their cellphones. The research team used a statistical method to categorize patients into four distinct groups based on how their pain evolved over time. These groups ranged from those who experienced low levels of pain to those who suffered from high, unremitting pain. This categorization allowed the scientists to see distinct patterns of recovery or non-recovery.

The analysis revealed a strong association between a history of childhood adversity and the trajectory of pain recovery. Individuals who reported higher levels of childhood trauma were statistically more likely to belong to the group with high, unremitting pain. The data showed that as the severity of past trauma increased, the likelihood of chronic physical pain also rose.

The study found that not all types of childhood difficulty had the same impact on adult pain. Physical abuse, emotional abuse, and bullying emerged as the strongest predictors of poor pain recovery. The authors noted that “physical abuse, emotional abuse, and bullying being the strongest predictors of high pain class assignment.” Physical and emotional neglect did not show a statistically significant link to the pain trajectories in the final adjusted models.

The researchers calculated the potential impact of eliminating these early stressors. Their statistical models suggested that if early life adversity were removed from the population, there could be a substantial reduction in the number of people experiencing high chronic pain. This finding highlights the long-term physical health consequences of child maltreatment.

To verify that these findings had a biological basis rather than just a psychological one, the team conducted parallel experiments using Sprague Dawley rats. Animal models allow scientists to control environmental variables that are impossible to isolate in human subjects. This approach helps confirm that the observed effects are driven by physiological changes.

The researchers created a model of early life adversity for the animals. They limited the nesting material available to mother rats and their pups for a brief period after birth. This shortage induces stress in the mother, which affects her interactions with her offspring and creates a stressful environment for the developing pups.

Once these rats reached adulthood, the researchers exposed them to a stressful event designed to mimic the traumatic experiences of the human participants. This procedure, known as single prolonged stress, involves temporary physical restraint and forced swimming. It is a standard method used to induce symptoms similar to post-traumatic stress in animals.

The scientists then measured the animals’ sensitivity to physical touch to gauge their pain levels. They used an electronic device to apply light pressure to the rats’ paws. The researchers recorded the amount of pressure required to make the animal pull its paw away.

The results from the animal experiments mirrored the trends seen in the human participants. Rats exposed to the stressful bedding conditions as pups displayed higher baseline sensitivity to touch as adults compared to rats raised in standard conditions. This suggests that the early stress had already altered their sensory processing before any adult trauma occurred.

The effect became even more pronounced after the adult stress exposure. Rats with a history of early life adversity remained sensitive to touch for a longer duration than the control group. While the control rats eventually recovered from the stress-induced sensitivity, the rats with early adversity continued to show signs of heightened pain response.

The authors reported that “neonatal limited bedding combined with SPS caused increased baseline sensitivity and prolonged mechanical hypersensitivity.” This prolonged sensitivity in the animals parallels the unremitting pain observed in the human subjects. The animal model provides a controlled environment to study the phenomenon free from the confounding factors present in human lives.

The researchers acknowledged several limitations in their work. The human participants provided details about their childhood experiences retrospectively. This reliance on memory can introduce inaccuracies or bias. Additionally, the study did not pinpoint the exact age at which the childhood adversities occurred.

The developmental timing of stress may play a role in how the nervous system adapts. Different stages of brain development may be more or less susceptible to specific types of stress. The current human data did not allow for a granular analysis of timing.

The animal model also had limitations. The researchers measured a reflexive response to physical touch. This measurement serves as a proxy for pain but does not capture the full emotional and cognitive complexity of the human pain experience. Human pain involves suffering and interference with daily life that a simple reflex test cannot measure.

Furthermore, the exact biological mechanisms linking the early stress to the later pain remain to be fully described. The study establishes that the link exists and can be replicated, but it does not explain exactly how the change occurs at a cellular level. It is unclear if the changes reside primarily in the brain, the spinal cord, or the peripheral nerves.

The authors suggest that future research should investigate these biological pathways. Potential areas of study include changes in the immune system and the neuroendocrine system. Previous research has hinted that early stress may create a state of low-grade inflammation that persists into adulthood.

Other possibilities include changes in neuroplasticity. Early stress might alter how the nervous system rewires itself, making it more prone to becoming “stuck” in a pain state. Identifying these mechanisms is a necessary step toward developing medical treatments.

Understanding the biological roots of this vulnerability could lead to new therapeutic strategies. If doctors can identify patients with a history of early adversity immediately after a car crash, they might offer different interventions. These interventions could target the specific physiological pathways that prevent recovery.

This translational approach helps bridge the gap between psychology and physiology. It reinforces the concept that mental trauma and physical pain are deeply interconnected. The findings emphasize the need for a holistic approach to treating trauma survivors.

The study, “Early life adversity increases risk for chronic posttraumatic pain, data from humans and rodents,” was authored by Lauren A. McKibben, Alice Woolard, Samuel A. McLean, Ying Zhao, Taanvii Verma, Jacqueline Mickelson, Hongxia Lu, Jarred Lobo, Stacey L. House, Francesca L. Beaudoin, Xinming An, Jennifer S. Stevens, Thomas C. Neylan, Tanja Jovanovic, Laura T. Germine, Scott L. Rauch, John P. Haran, Alan B. Storrow, Christopher Lewandowski, Phyllis L. Hendry, Sophia Sheikh, Christopher W. Jones, Brittany E. Punches, Lauren A. Hudak, Jose L. Pascual, Mark J. Seamon, Claire Pearson, David A. Peak, Roland C. Merchant, Robert M. Domeier, Niels K. Rathlev, Brian J. O’Neil, Leon D. Sanchez, Steven E. Bruce, John F. Sheridan, Ronald C. Kessler, Karestan C. Koenen, Kerry J. Ressler, and Sarah D. Linnstaedt.