Theeffectsofphotobiomodulationandtranscutaneouselectricalnervestimulationonchronicneckpain:Adouble-blind,randomized,sham-controlledtrial

Chronic neck pain affects millions worldwide and leads to significant disability and healthcare costs. Photobiomodulation (PBM) therapy using low-level laser and transcutaneous electrical nerve stimulation (TENS) are commonly used treatments, but their individual effectiveness remains unclear and no studies have compared them directly or investigated whether combining them provides better results. This matters because these treatments work through different biological pathways - PBM may reduce inflammation and promote healing at the cellular level, while TENS blocks pain signals through the nervous system. Understanding whether one is superior or if combining them enhances pain relief could improve treatment outcomes for people with chronic neck pain.

Researchers conducted a rigorous 4-arm study with 144 adults who had chronic neck pain lasting at least 3 months. Participants were randomly assigned to one of four groups: PBM plus TENS combination, PBM alone, TENS alone, or sham (fake) treatment. Everyone received 10 treatment sessions over 2 weeks. The PBM used infrared laser at 808 nanometers wavelength applied for 50 seconds to painful areas.

TENS delivered electrical stimulation at 100 Hz for 30 minutes at a comfortable but strong intensity. Sham treatments looked and felt real but delivered no therapeutic energy. Researchers measured pain intensity at rest and during movement, pressure pain sensitivity using an algometer at multiple neck and shoulder points, and various other outcomes including neck disability and quality of life. Importantly, both participants and evaluators were blinded to which treatment was real or fake.

The study found mixed results depending on the type of pain measured. For pain at rest - the main outcome - none of the treatments showed significant improvement compared to sham treatment. However, the combination of PBM plus TENS was significantly better than PBM alone and sham treatment for reducing pain during movement, with improvements of 1-2 points on a 10-point scale. The combination also improved participants' global perception of recovery and reduced local hyperalgesia (increased pain sensitivity) compared to individual treatments.

TENS alone was particularly effective at reducing both local and distant hyperalgesia, suggesting it may have effects throughout the nervous system. Most participants completed all 10 sessions, with attendance rates ranging from 81-93% across groups.

For patients with chronic neck pain, this study suggests that neither PBM nor TENS alone is particularly effective for reducing resting pain intensity. However, combining these treatments may provide modest benefits for pain experienced during movement and may help reduce hypersensitivity in painful areas. TENS appears to be the more effective individual treatment, particularly for reducing pain sensitivity. The clinical significance of these improvements is modest - while statistically significant, the changes may not represent dramatic pain relief that patients would strongly notice in daily life.

This research fills an important gap by being the first to directly compare these common treatments and test their combination. For clinicians, the results suggest these treatments should not be first-line therapies for chronic neck pain, but the combination approach might be considered as part of a broader treatment plan, particularly for patients whose pain worsens with movement.