The lessening of pain sensitivity achieved with spinal manipulation therapy (SMT) occurs as a result of the treatment and not as much from a placebo effect caused by the expectation of receiving SMT, according to a study published in The Journal of Pain.
Spinal manipulative therapy has been shown to reduce the severity of low back pain in some patients. Improved understanding of its pain-relieving mechanisms could enhance clinical effectiveness.
Chronic low back pain is associated with altered pain processing, suggesting a mechanism related to central sensitization of pain. Central sensitization is considered a factor in the progression of acute pain to chronic pain and in the maintenance of chronic pain.
Researchers from the University of Florida investigated whether lessening of pain sensitivity attributed to SMT is specific to the procedure itself or occurs as a placebo effect from treatment expectation. Studies have shown that placebo is associated with robust analgesia produced by anticipation of pain relief.
Subjects for the study had low back pain and were recruited from the University of Florida campus. Participants underwent baseline pressure and thermal pain testing and were randomly assigned to SMT, placebo SMT, enhanced placebo SMT (same as placebo SMT except subjects were informed they would get SMT or a placebo intervention) or no intervention. The 110 study subjects had repeat mechanical and thermal pain sensitivity testing to measure immediate, within session, change in pain sensitivity.
Results showed that significantly more participants receiving the enhanced placebo SMT indicated good to excellent outcomes than those receiving standard placebo SMT or no treatment. A significant difference was not found between subjects receiving SMT and the enhanced placebo.
The authors concluded their findings reveal a mechanism of SMT unrelated to the expectation of receiving SMT, but from modulation of dorsal horn excitability and lessening of central sensitization. This suggests potential for SMT to be a clinically beneficial intervention.
American Pain Society. “Spinal manipulative therapy reduces central pain sensitization.” ScienceDaily. ScienceDaily, 25 February 2014. <>.