Chronic pain among veterans


A new study is the first to investigate brain connectivity patterns at rest in veterans with both chronic pain and trauma, finding three unique brain subtypes potentially indicating high, medium, and low susceptibility to pain and trauma symptoms.

The findings provide an objective measurement of pain and trauma susceptibility and could pave the way for personalized treatments and new therapies based on neural connectivity patterns.

Chronic pain and trauma often co-occur. However, most previous research investigated them in isolation and using subjective measures such as surveys, leading to an incomplete picture. A new study in Frontiers in Pain Research has filled in some of the blanks.

It found three unique brain connectivity signatures that appear to indicate veteran susceptibility or resilience to pain and trauma, regardless of their diagnostic or combat history. The study could pave the way for more objective measurements 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 concern, especially among veterans,” said first author Prof. Irina Strigo of the San Francisco Veterans Affairs Health Care Center. “Moreover, chronic pain sufferers almost never present with a single disorder, but often with multiple co-morbidities, such as trauma, post-traumatic stress, and depression.”

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 measurements such as questionnaires, rather than objective measurements such as brain scans.

Identifying brain connectivity signatures of pain and trauma

Taking a different approach, the researchers behind this new research studied a group of 57 veterans with both chronic back pain and trauma. The group had quite varied 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 connection signatures, 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 divisions were comparable to the severity of the veterans’ symptoms, 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 fallout from pain and trauma, and also included natural pain reduction capabilities.

Conversely, the high symptom group demonstrated brain connection patterns that may have increased their chances of anxiety and catastrophizing when experiencing pain.

Interestingly, based on self-reported pain and trauma symptoms, the medium symptom group was largely similar to the low symptom group. However, the medium symptom group showed differences in their brain connectivity signature, which suggested that they were better at focusing on other things when experiencing pain, reducing its impact.

Putting the findings into future practice

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

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

So far, the researchers don’t know whether the neural hallmarks they found represent a vulnerability to trauma and pain or a consequence of these conditions. However, the technique is interesting, as it provides an objective and unbiased hallmark of pain and trauma susceptibility or resilience. It does not rely on subjective measures such as the surveys. In fact, subjective measurements of pain in this study would not differentiate between the low and medium groups.

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

The hypothesis that veterans and nonveterans were expected to demonstrate improvements in pain-related domains at discharge was supported by the results of the present study. Significant improvements in depressive symptoms, pain-related disability, pain acceptance, sensitivity to pain traumatization, stages of change, and a number of pain coping domains were found among veterans and nonveterans. Veterans experienced significantly greater improvements than nonveterans in anxiety, pain catastrophizing, recent bothersome symptoms, kinesiophobia, task persistence, and pre-contemplation and action stages of pain.

Among all patients, lower levels of depressive symptoms were observed at discharge from the program. This improvement can be attributed to the integration of activities designed to reduce depression symptoms in the 4-week intensive MGD program. On average, all patients also endorsed lower pain-related interference in family and home responsibilities, recreation, social activity, occupation, sexual behavior, self-care, and life support activity at discharge. These findings align with previous research, because depressive symptoms and disability have been shown to decrease after attending similar pain management programs.12,40

All patients improved on average on all four pain stages of change, essential in pain management, because changes in patients’ attitudes in adopting a pain self-management approach can predict long-term function.41 For the pre-contemplation and action stages, veterans demonstrated significantly greater improvements than nonveterans. Reductions in pre-contemplation are predictive of lower depressive symptoms, and increases in action are predictive of lower pain severity.41

Patient adjustment can be further predicted by patients’ scores on the coping strategies of guarding, asking for assistance, relaxation, and task persistence (CPCI).42 Improvements were observed for all patients on all of these scales except for task persistence. For task persistence, only veterans changed at discharge. Their higher scores at admission may be due to their need to complete tasks irrespective of pain given their extensive military disciplinary training. Their reduction in scores at discharge reflects a positive and adaptive change for veterans.

Both veterans and nonveterans also improved significantly on their sensitivity to pain traumatization as indicated by the differences in SPTS scores between admission and discharge. Nonveterans had higher SPTS scores at admission and discharge, aligning with the fact that there were significantly more PTSD diagnoses among veterans in this study. Moreover, this finding is consistent with similar differences in anxiety symptoms, because the SPTS focuses on anxiety-related cognitive, emotional, and behavioral reactions to pain.12 Anxiety levels among veterans decreased on average at discharge from the program, whereas nonveterans made a smaller, nonsignificant improvement. A potential source of anxiety for nonveterans could be anticipating returning to work, considering that their continued chronic pain could be a source of anxiety, because only seven veterans and 23 nonveterans were employed at admission. Moreover, nonveterans may also be experiencing their unresolved litigation cases as sources of stress and anxiety.

The finding of improvement in pain catastrophizing in all patients supports the literature, because behavioral interventions have been shown to decrease negative psychological states, including depression and pain catastrophizing.40 Significantly greater improvements in pain catastrophizing among veterans suggest that being a veteran may influence perspectives on pain, explaining the difference between groups. Small to moderate benefits for catastrophic thinking in addition to depression, anxiety, and disability have been reported in the literature.41 A potential explanation for the significantly greater improvements made by veterans at discharge could be a result of greater pain chronicity. Because veterans have, on average, experienced chronic pain for a significantly greater amount of time compared to nonveterans, they may have developed strategies to stabilize negative mindsets. This hypothesis is also supported by our pain acceptance findings. Even though both veterans and nonveterans showed an increase in acceptance of their chronic pain condition, a greater increase in pain acceptance was found among veterans. The difference in pain chronicity between groups may explain the demographic difference that veterans are higher users of primary care in comparison to nonveterans, as displayed in Table 1. Because veterans have had pain for longer and their pain is often more severe and complex, with comorbidities such as PTSD, a greater number of medical visits is expected.43

As a result of the teachings and practices integrated within the 4-week MGD program such as fitness education and daily fitness sessions, the finding that all participants reported lower levels of kinesiophobia at discharge is expected.44 Even though improvement in kinesiophobia has also been demonstrated in previous research, the present study found a greater difference in kinesiophobia scores among veterans.12 This difference may be explained by demographic differences in employment status and the risk of injury at work, because a higher proportion of nonveterans than veterans were employed. Lower levels of fear of re-injury among veterans may be because the majority are retired and do not expect to return to work.

Aligning with the expectation that patients would have an improved experience with their pain condition as a result of the program, both veterans and nonveterans endorsed lower levels of recent bothersome symptoms at discharge. However, a significant difference in scores between admission and discharge was only found in the veteran group, indicating that, on average, the program was especially effective for veterans. These results add to the literature, because Jiwani and Hapidou’s study found no significant improvements in bothersome symptoms for veteran and nonveteran groups.12

Program evaluation scores were found to be highly correlated between patients and their case managers (see Appendix D), providing evidence that these discharge questionnaires are valid evaluations of improvement at the end of the program. Both veterans and nonveterans improved in pain-related psychological measures, and self-reported evaluations also attested to these improvements. No differences were found between how veterans and nonveterans evaluated their own improvement in physical, emotional/mental, and social domains. However, case managers evaluated veterans as showing greater improvement than nonveterans on these domains. On the other hand, there was no difference in patient satisfaction between veterans and nonveterans, ultimately supporting that, irrespective of referral source, the 4-week MGD program is effective for all participants in this sample.

A strength of this study is that a variety of psychometric measures were utilized to assess pain on multiple dimensions, prospectively providing clinicians with a comprehensive evaluation of patients’ progress through the 4-week program. By comparing veteran pain outcomes to those of their nonveteran counterparts, this study contributes to the literature because results align with previous findings and provide more insight into pain management among veterans.12,40

Limitations of the present study include unknown confounders due to the reliance on retrospective sources of data. However, it was not feasible to conduct this study as a randomized controlled trial because the independent variable of group membership (veteran or nonveteran) cannot be randomized. Additionally, self-reported data are subject to misreporting, resulting in bias. Thus, further research should include objective measures such as functional magnetic resonance imaging or physical therapy outcomes.

Even though the psychometric measures utilized in this study are all valid and reliable, for the CES-D measure, an amended analysis could have been conducted to exclude several items that have demonstrated psychometric difficulties in previous studies, as recommended by Carleton et al.45 Additionally, the sample size of this study was limited to 136 patients due to the number of veterans who completed the program. The small sample size relative to the high number of variables examined may have limited the results of the study by introducing potential selection bias, impacting the generalizability of findings. Thus, this research would benefit from a replication study with a larger sample size. A follow-up study is currently underway on the 4-week MGD program to determine the extent to which treatment effects persist over time.

reference link :

More information: Irina A. Strigo et al, Understanding pain and trauma symptoms in Veterans from resting state connectivity: unsupervised modeling, Frontiers in Pain Research (2022). DOI: 10.3389/ … ain.2022.871961/full


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