According to the Centers for Disease Control and Prevention (CDC), chronic pain affects around
1 in 5 adults in the United States.
Almost half of these people report that pain frequently limits their day-to-day activities.
Scientists have linked chronic pain to opioid addiction, anxiety, depression, and reduced quality
of life, among other things.
Over the years, researchers have attempted to understand chronic pain by approaching it from
For instance, some have explored the sociological aspects of chronic pain, searching for societal
risk factors like employment status. If you do more manual labor, you are more likely to get hurt.
Others have looked at the role of psychological traits. For instance, according to the authors of
the latest study, some older studies have concluded that catastrophizing about pain and fear of
pain are both strong predictors of chronic pain.
In fact, the authors explain that many now consider psychological factors better predictors of
chronic pain disability than the actual injury itself."
However, few studies attempt to mesh together psychology, brain activity, and economic factors.
The latest study paper, which now appears in the journal PLOS Biology, set out to knit the
strands together and formulate a way to develop a more holistic view of chronic pain.
Firstly, the team assessed how psychological traits linked to chronic pain interact with general
personality types. Next, they used functional MRI (fMRI) scans to see if they could identify
chronic pain-related patterns of activity.
The scientists took data from a randomized controlled trial that included people with chronic
back pain. All participants filled out in-depth questionnaires that collected information about
personality traits and socioeconomic factors.
For the study, 62 participants visited the laboratory on six occasions; on four of those occasions,
they underwent a resting-state fMRI scan. Another 46 participants completed the questionnaires
but did not have a brain scan.
Resting-state fMRI scans to measure brain activity when a person is not engaged in a cognitive
task. These scans provide insight into the brain’s functional organization.
The study authors found four clusters of characteristics, or dimensions, within the participants.
Two of these dimensions, which they named Pain-trait and Emote-trait, seemed particularly
Pain-trait encompasses the traditional factors that scientists already believe increase the severity
of chronic pain, such as catastrophizing about pain and fear of pain. Individuals with this
dimension were more likely to report worse pain.
Emote-trait, however, appeared to be protective; this dimension includes optimism, lower levels
of neuroticism, and a capacity for mindfulness.
According to the authors, Emote-trait seems to offset and counteract the negative emotional
impact of chronic pain.
These dimensions were also reflected in resting-state fMRI scans and matched what the authors
refer to as neurotraits. These neurotraits appeared to be stable, and the researchers observed
them in all four brain scans.
The networks that became activated as part of these neurotraits were not confined to brain areas
that deal with pain. Instead, they spread to regions that scientists believe play a part in
catastrophizing, for instance.
The team found that people with higher incomes were protected against chronic pain. Those with
lower incomes reported higher pain scores and increased disability. These results echo those of
previous work in a similar vein.
For instance, a study that looked at the role of financial stability on people’s experience of
chronic pain concluded that economic hardship was associated not only with greater exposure to
daily financial worries but also with greater vulnerability to pain on days when daily financial
worries were experienced.
Regardless, they conclude that the findings bolster the idea that chronic pain experience is not
only rooted in biology but also intimately embedded in society.
The authors do note several limitations of the study. For example, they excluded people with
moderate or severe depression, which, they believe, might limit the generalizability of the
In future projects, the researchers would like to add more depth to their questionnaires; this study
did not account for a wide range of potentially important factors, such as working environment,
marital status, and access to healthcare.
Also, the study included only a small number of participants. It is possible that the findings do
not extend to the population at large.
Finally, the protective neurotraits mentioned are more likely to drive people to success, meaning
that pinning the blame on poverty is reverse causation.
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