Pain Catastrophizing Is Associated With Reduced Neural Response to Monetary Reward
Key findings
- This study investigated neural mechanisms associated with pain catastrophizing by reviewing baseline functional MRI scans from a clinical trial of cannabis for medical symptoms in patients with self-reported pain, insomnia, and/or anxiety/depression symptoms
- During MRI, the 94 participants included in the current analysis had completed the monetary incentive delay task, which is designed to elicit activation of the reward system
- Higher scores on the Pain Catastrophizing Scale were associated with decreased activation in the right caudate to positive feedback during the task, independent of self-reported depression symptoms
- This work underscores the importance of accounting for pain catastrophizing when studying affective components of pain that may affect brain circuitry
Pain catastrophizing—an exaggerated negative cognitive–affective response to anticipated or actual pain—can have numerous adverse outcomes, including amplified pain intensity and the development of chronic pain. It is a key target in many psychological treatments for pain.
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Altered reward processing has been observed in adults with chronic pain and might represent a neural target for treatment. Massachusetts General Hospital researchers wondered whether this negative emotional state from pain catastrophizing might similarly influence the brain's response to rewarding stimuli.
In Frontiers in Pain Research, they present evidence supporting their hypothesis. Megan E. Cooke, PhD, postdoctoral researcher, Jodi M. Gilman, PhD, director of neuroscience in the Department of Psychiatry's Center for Addiction Medicine, and colleagues found pain catastrophizing is associated with altered striatal function independently of depression symptoms and pain intensity.
Methods
The study leveraged data from a randomized trial of medical cannabis, previously published in JAMA Network Open, in individuals with a wide range of pain, insomnia, and/or anxiety/depression symptoms. Functional MRI scans were available on 94 participants (68% female, mean age 36) who had completed various questionnaires at baseline, including:
- The pain severity subscale of the Brief Pain Inventory Short Form
- The Pain Catastrophizing Scale (PCS)
- The depression subscale of the Hospital Anxiety and Depression Scale (HADS-Dep)
During MRI, participants had completed the monetary incentive delay task, a standard method of measuring activation of the reward system. There were three trial types:
- Win money ($0.20 or $5.00)
- Lose money ($0.20 or $5.00)
- No incentive ($0)
Participants saw a cue (pink circle, yellow square, or blue triangle) at the beginning of trials that indicated the valence (reward, loss, or neutral) and the amount of money at stake. To gain money or avoid losing money, they had to press a response button while the cue was on the screen. They received feedback on accuracy after each trial.
An adaptive algorithm ensured participants experienced 30 positive feedback trials (split between reward, loss and neutral) and 20 negative feedback trials, on average. After the scan, participants completed a questionnaire reporting what their mood was when they saw each type of cue (energetic, excited, fearful, unhappy, etc.).
Results
The key findings were:
- The score on the PCS was significantly correlated with the score on the HADS-Dep (r=0.53; P = 4.08 × 10−8) and not with the pain intensity score
- Higher PCS scores were associated with decreased positive mood ratings across all trial types and were not associated with negative mood ratings
- Participants with higher PCS scores showed less activation in the right caudate in response to feedback about successful trials
- Mediation analyses indicated the relationship between pain catastrophizing and caudate activation was distinct from an effect of depression on reward activation
- However, the effects of pain catastrophizing were somewhat diminished when controlling for depression symptoms, suggesting a shared association of these inter-related variables on reward processing
Continued Scrutiny Needed
Consistent with previous research, these findings suggest individuals with high levels of pain catastrophizing express dampened positive affective responses. Pain catastrophizing appears to be an important factor to consider when assessing brain mechanisms of reward.
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