At any given time, 8% of adults experience chronic low back pain. Some studies indicate that mindfulness meditation can alleviate the pain and disability associated with this condition. However, the precise mechanism behind this benefit is not clear. Does it involve engaging the body’s endogenous opioid system, teaching individuals to become psychologically non-reactive, or operating through a placebo effect?

Khatib et al. [Neuropsychopharmacology] tested the effects of mindfulness meditation versus sham mindfulness meditation, both with and without the opioid antagonist Naloxone, on evoked chronic low back pain.

The researchers randomly assigned 71 patients (average age = 46 years; 51% female; 87% Caucasian) experiencing chronic low back pain persisting for at least 3 months to either mindfulness or sham mindfulness meditation groups. Both groups participated in four 20-minute meditation training sessions.

The mindfulness training focused on accepting thoughts and feelings, recognizing their transient nature, and returning attention to the breath. In contrast, sham meditation training emphasized breathing slowly and deeply in a meditative posture without additional instructions.

Participants met with researchers seven times. The first session was a pre-intervention assessment. During sessions 1, 6, and 7, the researchers induced pain in participants using a straight leg raise procedure. Participants lay supine while the researchers raised one of their legs to a 90-degree angle while keeping the knee straight. Participants alerted researchers when their pain rose by 2 points on a 10-point scale. Researchers continued to raise their legs up to 6 times until a 2-point increase in pain was induced. Patients then rated post-leg raise pain on a 10-point scale.  

Participants practiced mindfulness or sham mindfulness meditation during sessions 2-5 and completed questionnaires of pain severity, catastrophizing, and disability before and after each session. During sessions 6 and 7, pain was evoked by straight leg raises after seven minutes of rest.

Participants then received either intravenous Naloxone (which blocks the endogenous opioid system) or saline (a placebo). Participants then meditated or sham meditated for 7 minutes before once again reporting evoked pain both before and after leg raises. 

The results indicated that both mindfulness and sham meditation significantly reduced evoked pain following both Naloxone and saline administration. However, the mindfulness group reported significantly lower evoked pain after rest, Naloxone, and saline compared to the sham meditation group (partial η2= .09).

Sixty percent of the mindfulness group reported practicing non-reactive attention during meditation, while 20% of the sham mindfulness group did. Practicing non-reactive attention during meditation was associated with lower evoked pain in the mindfulness group (r = -.35) but not in the sham group (r = .04).

The study shows that both mindfulness and sham meditation effectively decrease evoked pain in chronic low back pain patients. However, mindfulness meditation outperformed sham meditation in this aspect.

The finding that Naloxone fails to block this effect suggests that meditation does not rely on endogenous opioids to achieve pain reduction. This does not rule out contributions from non-opioid systems like the dopaminergic, glutaminergic, or endocannabinoid systems. The correlation between non-reactive attention and pain reduction suggests that mindfulness meditation’s pain-reduction effect is due, at least partially, to non-reactive reappraisal processes.

Reference:

Khatib, L., Dean, J. G., Oliva, V., Riegner, G., Gonzalez, N. E., Birenbaum, J., Cruanes, G. F., Miller, J., Patterson, M., Kim, H.-C., Chakravarthy, K., & Zeidan, F. (2023). The role of endogenous opioids in mindfulness and sham mindfulness-meditation for the direct alleviation of evoked chronic low back pain: A randomized clinical trial. Neuropsychopharmacology. 

Link to study