Discovery in the brains of military veterans sheds light on the neurobiological mechanisms behind chronic pain and trauma

Discovery in the brains of military veterans sheds light on the neurobiological mechanisms behind chronic pain and trauma

Discovery in the brains of military veterans sheds light on the neurobiological mechanisms behind chronic pain and trauma

A new study is the first to examine brain connectivity patterns at rest in veterans with both chronic pain and trauma, finding three unique brain subtypes that may indicate high, medium, and low sensitivity to pain and trauma symptoms. The findings provide an objective measure of pain and trauma sensitivity and could pave the way for personalized treatments and new therapies based on neural connectivity patterns.

Chronic pain and trauma often coexist. However, most previous studies have isolated them and examined them using subjective measures such as surveys, resulting in an incomplete picture. A new study in Limits in pain research has filled in some blanks. It found three unique features of brain connectivity that seem to indicate veterans’ sensitivity or resilience to pain and trauma, regardless of their diagnostic or combat histories. The research could pave the way for more objective measures of pain and trauma, leading to targeted and personalized treatments.

Chronic pain and trauma are linked, but not studied together

“Chronic pain is a major public health problem, especially among veterans,” said first author Prof. Irina Strigo of the San Francisco Veterans Affairs Health Care Center. “In addition, chronic pain sufferers almost never present with a single condition, but often with multiple co-morbidities, such as trauma, post-traumatic stress and depression.”

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Researchers already understand that both pain and trauma can affect connections in our brains, but no one had studied this in the context of co-occurring trauma and pain. Much pain and trauma research also relies on subjective measures, such as questionnaires, rather than objective measures, such as brain scans.

Identifying brain connectivity signatures of pain and trauma

Taking a different approach, the researchers behind this new study studied a group of 57 veterans with both chronic back pain and trauma. The group had quite a variety of symptoms in terms of pain and trauma severity. By scanning the veterans’ brains using functional magnetic resonance imaging, the researchers identified the strength of connections between brain regions involved in pain and trauma. They then used a statistical technique to automatically group the veterans based on their brain connections, regardless of their self-reported pain and trauma levels.

Based on the veterans’ brain activity, the computer automatically divided them into three groups. Strikingly, these classifications were comparable to the veterans’ symptom severity, and they fell into a low, medium, or high symptom group.

The researchers hypothesized that the pattern of brain connections found in the low-symptom group allowed veterans to avoid some of the emotional consequences of pain and trauma, and also included natural pain-reduction capabilities. Conversely, the high-symptom group showed brain-connection patterns that may have increased their chances of fear and catastrophizing when experiencing pain.

Interestingly, based on self-reported pain and trauma symptoms, the moderate symptoms group was largely comparable to the low symptoms group. However, the medium symptom group showed differences in their brain connectivity signature, suggesting that they were better able to focus on other things when experiencing pain, reducing its impact.

Applying the findings in future practice

“Despite the fact that the majority of subjects within each subgroup had a comorbid diagnosis of pain and trauma, their brain connections differed,” Strigo said.

“In other words, despite demographic and diagnostic similarities, we found neurobiologically distinct groups with different mechanisms for coping with pain and trauma. Neurobiologically based subgroups may provide insight into how these individuals will respond to brain stimulation and psychopharmacological treatments.”

So far, the researchers don’t know whether the neural features they found represent a vulnerability to trauma and pain or are a result of these conditions. The technique is interesting, however, because it provides an objective and unbiased characteristic of pain and trauma sensitivity or resilience. It does not rely on subjective measurements like the surveys. In fact, subjective measures of pain in this study would not distinguish between the low and medium groups.

Techniques that use objective measures, such as brain connectivity, appear more sensitive and can provide a clearer overall picture of a person’s resilience or susceptibility to pain and trauma, guiding personalized treatment and paving the way for new treatments.