Neural Mechanisms of Acceptance and Commitment Therapy for Chronic Pain: A Network-Based fMRI Approach

Abstract

Over 100 million Americans suffer from chronic pain (CP), which causes more disability than any other medical condition in the U.S. at a cost of $560-$635 billion per year (IOM, 2011). Opioid analgesics are frequently used to treat CP. However, long term use of opioids can cause brain changes such as opioid-induced hyperalgesia that, over time, increase pain sensation. Also, opioids fail to treat complex psychological factors that worsen pain-related disability, including beliefs about and emotional responses to pain. Cognitive behavioral therapy (CBT) can be efficacious for CP. However, CBT generally does not focus on important factors needed for long-term functional improvement, including attainment of personal goals and the psychological flexibility to choose responses to pain. Acceptance and Commitment Therapy (ACT) has been recognized as an effective, non-pharmacologic treatment for a variety of CP conditions. However, little is known about the neurologic mechanisms underlying ACT. We conducted an ACT intervention in women (n=9) with chronic musculoskeletal pain. Functional magnetic resonance imaging (fMRI) data were collected pre- and post-ACT, and changes in functional connectivity (FC) were measured using Network-Based Statistics (NBS). Behavioral outcomes were measured using validated assessments such as the Acceptance & Action Questionnaire (AAQ-II), the Chronic Pain Acceptance Questionnaire (CPAQ), the Center for Epidemiologic Studies Depression Scale (CES-D), and the NIH Toolbox Neuro-QoLTM (Quality of Life in Neurological Disorders) scales. Results suggest that, following the four-week ACT intervention, participants exhibited reductions in brain activation within and between key networks including self-reflection (default mode, DMN), emotion (salience, SN), and cognitive control (frontal parietal, FPN). These changes in connectivity strength were correlated with changes in behavioral outcomes including decreased depression and pain interference, and increased participation in social roles. This study is one of the first to demonstrate that improved function across the DMN, SN, and FPN may drive the positive outcomes associated with ACT. This study contributes to the emerging evidence supporting the use of neurophysiological indices to characterize treatment effects of alternative and complementary mind-body therapies.

Network Analysis of Induced Neural Plasticity Post-Acceptance and Commitment Therapy for Chronic Pain

“…This collection of 10 nodes and 10 edges showed reduced connectivity from pre-ACT to post-ACT ( Figure 2 A; t > 2.5 p = 0.05). This network is representative of the same finding in our previous report [ 21 ]. We subsequently tested for effects of ACT on the 10 nodes identified in the previous analysis ( Figure 2 A) combined with the seven pain nodes (17 nodes total).…”

“…Nine female participants (age 47.59 years ± 16.54 years; eight right-handed) completed the entire four-week ACT protocol of Aytur and colleagues’ study [ 21 ] after being recruited through community-based health care clinics and providing their informed consent. The study (#6991) was approved by the University of New Hampshire Institutional Review Board on July 19, 2018.…”

“…In our initial report [ 21 ] we tested for changes in brain networks underlying ACT-related outcomes in those with CMP using only triple network nodes without the inclusion of pain nodes ( t > 2.1 for the 101 nodes of the DMN, FPN, and SN). We observed effects in 10 nodes out of 101 triple network nodes and used those same 10 for the following analysis in conjunction with Waller and colleagues’ [ 35 ] pain matrix of seven nodes found via ALE (17 nodes in total).…”

“…The current investigation builds upon Aytur and colleagues’ work (under review, [ 21 ]) on behavioral changes and neurological changes in connectivity within and between the DMN, FPN, and SN as a result of four weeks of Acceptance and Commitment Therapy (ACT) for chronic pain. Hayes and colleagues describe ACT as a “third generation approach” that is particularly sensitive to psychological phenomena and emphasizes contextual changes and directly targeted approaches to create a broad and flexible range of mental capabilities [ 22 ].…”

“…Prior to this study, as well as Aytur and colleagues’ study [ 21 ], little was known about how the brain can change in response to specific interventions in certain disease states, such as CMP. The extent to which ACT interacts with the hypothesized neural systems underlying chronic pain was also unknown.…”