The effects of 12 weeks of chiropractic spinal adjustments on physiological biomarkers in adults: A pragmatic randomized controlled trial.

The short version

This pragmatic randomized controlled trial with 106 adults explored whether chiropractic spinal adjustments change measurable biological markers, not just how patients feel. Researchers tracked three systems: neuroplasticity (the nervous system's capacity to adapt, measured via brain-derived neurotrophic factor or BDNF — a protein that supports brain and nerve health), stress response (measured through cortisol, the body's primary stress hormone, sampled from blood, saliva, and hair), and inflammation (tracked via cytokines like IL-6 and TNF-α, signaling proteins immune cells use to coordinate the body's inflammatory response). The goal was to see whether chiropractic care's known benefits for pain and function might trace back to changes at this biological level. Pain-free adults aged 20-60 with a history of recurrent (subclinical) spinal discomfort were randomly assigned to 12 weeks of chiropractic spinal manipulation — delivered about three times weekly by a registered chiropractor — or a closely matched sham procedure with no actual spinal thrust. Eighty-eight of the 106 enrolled completed the 12-week assessment. Blood, saliva, and hair samples were analyzed via laboratory immunoassay at baseline, 12 weeks, and a 16-week follow-up. Blinding worked well: 94% of participants in both groups believed they had received real chiropractic care. After 12 weeks, the chiropractic group showed meaningfully higher blood BDNF (up 150 units, p=0.009 — a strong statistical signal this wasn't due to chance) and higher IL-6 (p<0.001) than the sham group, alongside lower TNF-α at both 12 and 16 weeks (p=0.023 and p=0.028). The researchers interpret the IL-6 rise not as harmful inflammation but as a "myokine" effect — the same kind of signal muscles release after exercise — since it appeared alongside lower TNF-α and IFN-γ, the markers more classically tied to harmful inflammation. By 16 weeks, blood cortisol and IFN-γ were lower in the chiropractic group than sham, though this reflected the sham group's levels rising over that period more than a further chiropractic effect. Markers like CRP and several immune cell counts (CD4, CD8, CD56) showed no clear group differences. Only five participants reported mild, short-lived muscle soreness; no other adverse events occurred. This is among the first studies to track chiropractic's biological effects over months rather than single sessions, offering a possible mechanism — neuroplasticity, stress-hormone, and inflammation changes — behind chiropractic's reported clinical benefits. But the effects were modest, confidence intervals were wide, and the single-site Pakistani sample of 88 completers, with over 30% dropout by 16 weeks, limits how far these findings generalize. Larger trials that connect these biomarker shifts to actual pain relief and function are the next step.

Key findings

• In this 12-week randomized trial, adults receiving real chiropractic spinal adjustments showed a significant rise in brain-derived neurotrophic factor (BDNF, a protein that supports nerve and brain health) compared to those receiving sham (fake) chiropractic care.
• Inflammatory markers moved in a favorable direction for the chiropractic group: tumor necrosis factor-alpha (TNF-α, a pro-inflammatory signaling protein) was significantly lower at both the 12-week and 16-week marks.
• A rise in interleukin-6 (IL-6) in the chiropractic group was interpreted by the researchers as a muscle-repair signal similar to what happens after exercise, not a harmful inflammatory response, since more classic inflammation markers moved downward at the same time.
• Only five of 106 participants reported any side effect — mild, short-lived muscle soreness after the first session — and no other adverse events occurred over the 16-week study.
• These are modest, single-study findings from 88 completers in Pakistan; larger trials are needed before concluding these biomarker changes translate into better pain relief or function for patients.

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