Mindfulness-Based Analgesia or Placebo Effect? The Development and Evaluation of a Sham Mindfulness Intervention for Acute Experimental Pain

A synthesis of meta-analyses of mindfulness-based interventions in pain

ABSTRACT

Mindfulness interventions have become popular in recent decades, with many trials, systematic reviews, and meta-analyses of the impact of mindfulness-based interventions (MBIs) on pain. Although many meta-analyses provide support for MBIs, the results are more mixed than they at first appear. The aim of this umbrella review was to determine the strength of evidence for MBIs by synthesizing available meta-analyses in pain. We conducted a systematic search in 5 databases and extracted data from published meta-analyses as the unit of analysis. For each outcome, we reported the range of effect sizes observed across studies and identified the largest meta-analysis as the "representative" study. We separately analysed effect sizes for different pain conditions, different types of MBIs, different control groups, and different outcomes. We identified 21 meta-analyses that included 127 unique studies. According to Assessment of Multiple Systematic Review ratings, the meta-analyses ranged from very strong to weak. Overall, there was an impact of MBIs on pain severity, anxiety, and depression but not pain interference or disability. When conditions were considered in isolation, only fibromyalgia and headache benefited significantly from MBIs. Mindfulness-based interventions were more efficacious for pain severity than passive control conditions but not active control conditions. Only pain severity and anxiety were affected by MBIs at follow-up. Overall, our results suggest that individual meta-analyses of MBIs may have overestimated the efficacy of MBIs in a range of conditions. Mindfulness-based interventions likely have a role in pain management but should not be considered a panacea.

Effect of slow, deep breathing on visceral pain perception and its underlying psychophysiological mechanisms

BACKGROUND

Studies using somatic pain models have shown the hypoalgesic effects of slow, deep breathing. We evaluated the effect of slow, deep breathing on visceral pain and explored putative mediating mechanisms including autonomic and emotional responses.

METHODS

Fifty-seven healthy volunteers (36 females, mean age = 22.0 years) performed controlled, deep breathing at a slow frequency (6 breaths per minute), controlled breathing at a normal frequency (14 breaths per minute; active control), and uncontrolled breathing (no-treatment control) in randomized order. Moderate painful stimuli were given during each condition by delivering electrical stimulation in the distal esophagus. Participants rated pain intensity after each stimulation. Heart rate variability and self-reported arousal were measured during each condition.

KEY RESULTS

Compared to uncontrolled breathing, pain intensity was lower during slow, deep breathing (Cohen's d = 0.40) and normal controlled breathing (d = 0.47), but not different between slow, deep breathing and normal controlled breathing. Arousal was lower (d = 0.53, 0.55) and heart rate variability was higher (d = 0.70, 0.86) during slow, deep breathing compared to the two control conditions. The effect of slow, deep breathing on pain was not mediated by alterations in heart rate variability or arousal but was moderated by pain catastrophizing.

CONCLUSIONS AND INFERENCES

Slow, deep breathing can reduce visceral pain intensity. However, the effect is not specific to the slow breathing frequency and is not mediated by autonomic or emotional responses, suggesting other underlying mechanisms (notably distraction). Whether a long-term practice of slow, deep breathing can influence (clinical) visceral pain warrants to be investigated.

How do placebo effects contribute to mindfulness-based analgesia? Probing acute pain effects and interactions using a randomized balanced placebo design

ABSTRACT

Recent sham-controlled studies suggest placebo effects contribute to acute pain relief following mindfulness interventions. However, the specific effects of mindfulness processes and their interaction with placebo effects remain unclear. This study aimed to characterize the role of mindfulness and placebo processes underlying mindfulness-based pain attenuation. Both treatment (focused-attention mindfulness vs sham) and instruction ("told mindfulness" vs "told sham") were manipulated in a balanced placebo design. Changes in acute heat pain were evaluated in 153 healthy adults randomized to receive 6 x 20 minutes of one of the four treatment by instruction interventions or no treatment. Participants receiving any intervention demonstrated improved pain outcomes (unpleasantness, intensity and tolerance) relative to no treatment. The instruction manipulation increased expectation for pain relief in those told mindfulness relative to told sham, but there were no main effects or interactions of treatment or instruction on pain outcomes. However, irrespective of actual intervention received, the belief of receiving mindfulness predicted increased pain threshold and tolerance, with expectancy fully mediating the effect on pain tolerance. These findings suggest a lack of specific effects of mindfulness and instruction on acute pain. Nonetheless, participants' expectancies and beliefs about the treatment they received did predict pain relief. Together with the overall improvement following any intervention, these findings suggest that expectancy and belief may play a stronger role in attenuating acute pain in novices following brief mindfulness interventions than the actual mindfulness-specific processes or instructions delivered.

Harnessing Life's Slings and Arrows: The Science and Opportunities for Mindfulness Meditation During a Global Pandemic and Beyond

ABSTRACT

We are at a difficult time in history with societal increases in stress, loneliness, and psychopathology, along with high rates of obesity, sedentary lifestyles, and chronic pain. Mindfulness interventions offer promise to address these societal issues. However, in order to make best use of the opportunities revealed by our current challenges, we must: (1) tackle these issues head-on with inclusive, innovative, and creative experimental designs and interventions, and (2) collectively adhere to rigorous, high quality methods so as to provide an evidence-based integration of mindfulness interventions into mainstream medicine and public health.We find there are several areas for which important advances are happening, including sampling socially diverse populations, examining mechanisms of action, pain management, and health behaviors. Furthermore, rigorous methods, including measurement, causal inference from control groups, delivery and scalability of mindfulness interventions, and effect modifiers to determine who mindfulness programs work best for are also gaining traction. This special issue on Mindfulness: Biobehavioral Mechanisms and Health Outcomes attends to many of these issues, several of which are highlighted in this editorial perspective.