Research Review By Dr. Demetry Assimakopoulos©

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Date Posted:

December 2020

Study Title:

Trait Mindfulness Is Associated with Lower Pain Reactivity and Connectivity of the Default Mode Network

Authors:

Harrison R, Zeidan F, Kitsaras G et al

Author's Affiliations:

School of Psychology and Clinical Language Sciences, University of Reading, United Kingdom; Wake Forest School of Medicine, North Carolina, USA; Department of Psychology, Queen’s University, Ontario, Canada

Publication Information:

Journal of Pain 2019; 6: 645-654.

Background Information:

Mindfulness practice has been shown to reduce pain, as well as both the individual sensory-discriminative and affective-emotional components of pain. These findings are believed to be related to greater activation of brain areas associated with sensory and/or salience processing (1-3), and decreased activation in prefrontal cortical regions linked to evaluative and/or emotional responses (4, 5). These functional brain changes are believed to be associated with enhanced focus on the present moment and regulation of emotional responses.

Training of attentional focus (via mindfulness or meditative practices) has been demonstrated to be accompanied by activation in brain areas related to cognitive control and brain networks supporting self-referential processing, such as the Default Mode Network (DMN). Trait mindfulness (i.e. being mindful as part of a person’s disposition, or a ‘character trait’) is known to be associated with decreased activation across DMN nodes following short-term (< 1-month) and longer-term meditative practice. With this in mind, the authors of this study investigated whether untrained trait mindfulness is associated with differential responses to pain stimuli prior to any meditation training, and whether these intrinsic differences reflect differential patterns of resting-state functional connectivity.

Pertinent Results:

A greater degree of trait mindfulness was significantly associated with higher Heat Pain Thresholds (as characterized by requiring a more intense heat stimulus to induce a pain response; r = .43; P = .004) and lower pain catastrophizing scores (R = .59; P < .01). Conversely, pain catastrophizing and pain threshold were significantly predictive of trait mindfulness.

From the perspective of neuroimaging, connectivity between the precuneus and bilateral somatosensory cortices, and between the precuneus and prefrontal cortex were significantly associated with pain threshold (r = .46; P < .01 and r = .34; P = .02, respectively) and pain catastrophizing (r = .50; P < .01 and r = .31; P = .03, respectively).

Interestingly, pain catastrophizing was NOT significantly correlated with pain threshold (r = .22; P = .103). This might be a reflection of the use of a controlled, experimental pain stimulus (heat pain threshold), in a context where the stimulus demonstrates no threat of tissue damage and can be immediately stopped at any time.

Clinical Application & Conclusions:

This study demonstrated that even in the absence of any formal mindfulness training, practice or intervention, trait mindfulness is associated with individual differences in pain responsivity and characteristic patterns of functional connectivity within the brain. Specifically, trait mindfulness was associated positively with pain threshold and inversely with pain catastrophizing. Simply translated, as scores in Trait Mindfulness increase, pain thresholds increase, while scores on the Pain Catastrophization Scale (PCS) decrease.

Resting fMRI of those with higher trait mindfulness showed stronger functional connectivity between the Default Mode Network (precuneus) and somatosensory cortices, and weaker connectivity between the precuneus and the medial Prefrontal Cortex (mPFC). This finding may indicate that in the context of higher degrees of trait mindfulness, patients may increase their attention towards the immediate sensory aspects of pain, while decreasing their focus on maladaptive cognitions such as rumination and evaluation.

Reviewer’s note: Remember, pain is a multidimensional experience, consisting of sensory-discriminative, cognitive-evaluative and affective contributors. The somatosensory cortices are known to be involved in the sensory-discriminative aspects of nociceptive processing, while the mPFC is known to be involved in the cognitive-evaluative aspects of nociceptive processing.

These findings also suggest that trait mindfulness might function as a marker for dispositional individual differences in the ability to cope with pain. With this being said, the authors suggested that the Five-Facet Mindfulness Questionnaire (FFMQ) measuring trait mindfulness could provide information about how individuals cope with pain, and may be used to identify individuals who might need additional coping strategies.

Study Methods:

Thirty-six volunteers were recruited. Participants were excluded if they had active or historical diagnoses of chronic pain, current instances of acute pain, current substance abuse, uncorrected visual impairment or if they had practiced mindfulness in the past.

Each patient filled in the Pain Catastrophization scale (PCS) and the Five-Facet Mindfulness Questionnaire (FFMQ, which measures trait mindfulness) at baseline. Each patient then underwent neuroimaging that took place no more than 7-days after the initial session.

The patients were exposed to noxious heat stimulated by a heat thermode applied to the lower right calf. The authors used 2 assessments to measure heat pain threshold. The first method consisted of applying a heat thermode to the calf at an initial temperature of 32°C. The heat stimulus was increased by 0.5°C per second until the participant indicated that the stimulus was painful (known as Heat Pain Threshold). 4 trials were conducted, with an 8-second inter-stimulus interval. The average of the final 3-trials was taken as the Heat Pain Threshold.

The second assessment for pain threshold was then applied. Specifically, heat stimulation was applied at 32°C, and increased by 8°C per second to a 40°C peak, where it remained for 8 seconds. The participant was asked to indicate with a mouse whether the stimulus was painful. If they indicated “no” the subsequent trial was increased by 2°C. If they indicated yes, the temperature was decreased at half the interval size and the same pattern continued until 4-reversals of direction had been reached, at which point the program was terminated. The average of the final 2-trials was used as the individual’s level threshold. The results of each of the above-mentioned trials were well-correlated. The average of the above-mentioned processes to measure heat pain threshold were used as the participant’s threshold.

Functional MRI brain imaging was completed. The precuneus is a core DMN node and anatomic target for examining DMN processing (6, 7) – it was located in this study for analysis. The mean time series of all voxels within the precuneus were extracted and included as a regressor in the analysis of whole-brain functional connectivity.

Study Strengths / Weaknesses:

Strengths:

The authors utilized multiple methods of identifying a baseline Heat Pain Threshold, which improves the quality of the measurement. Additionally, the combination of sensory threshold testing with neuroimaging is not often performed in studies such as this, because it takes a lot of time and is costly. As such, we can see how different brain activation patterns might be associated with paper questionnaires and sensorial testing, which in turn, may enable clinicians to understand the underlying brain activation patterns associated with clinical findings.

Weaknesses:

The number of included subjects was low; sadly, this is typical of expensive neuroimaging studies such as this. It is also imperative for us as clinicians to understand that there is a great divide between what we see in studies such as these, and real-world clinical practice. With this being said, we must remember that pain perception is incredibly context specific. As such, the results of this study are limited to this controlled setting, within the confines of the exclusion criteria. Patients are much more complex in real-life. We should also separately note, that the correlations described in the results section, while statistically significant, were moderate in strength. Finally, we should understand that how this work translates into clinical practice is uncertain, as trait mindfulness is not typically something we account for. Is trait mindfulness something we should be measuring clinically, as a proxy for one’s ability to cope? Who knows?! Clearly, more research needs to be done in this area before it changes the way we practice, but this was an interesting addition to the literature nonetheless.

Additional References:

  1. Gard T, Hölzel BK, Sack AT et al. Pain attenuation through mindfulness is associated with decreased cognitive control and increased sensory processing in the brain. Cereb Cortex 2012; 22: 2692-2702
  2. Lutz A, McFarlin DR, Perlman DM, et al. Altered anterior insula activation during anticipation and experience of painful stimuli in expert meditators. Neuroimage 2013; 64: 538-546.
  3. Zeidan F, Martucci KT, Kraft RA, et al. Brain mechanisms supporting the modulation of pain by mindfulness meditation. J Neurosci 2011; 31: 5540- 5548.
  4. Hölzel BK, Lazar SW, Gard T, et al. How does mindfulness meditation work? Proposing mechanisms of action from a conceptual and neural perspective. Perspect Psychol Sci 2011; 6: 537-559.
  5. Zeidan F. Mindfulness meditation-related pain relief: Evidence for unique brain mechanisms in the regulation of pain. Neurosci Lett 2012; 520: 165-173.
  6. Sheline YI, Barch DM, Price JL et al. The default mode network and self-referential processes in depression. Proc Natl Acad Sci 209; 106:1942-1947.
  7. Utevsky AV, Smith DV, Huettel SA. Precuneus is a functional core of the default-mode network. J Neurosci 2014; 34:932-940.

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