Chronic pain affects at least 10% of the world’s population and even though it diminishes the productivity and quality of life of millions, it is under-treated by health systems across the world. Pain when it is treated, is managed with largely with medication that can have serious side effects. The key to better treatments of chronic pain may lie in new therapies like the use of green light-emitting diodes or LEDs that researchers from University of Arizona in the United States have been experimenting with.

The research team conducted a series of experiments on rats with neuropathic pain, a chronic pain caused due to damaged or dysfunctional nerve fibres. One group of rats were placed in clear plastic containers fixed with green LED strips that allowed their bodies to be bathed in green light. Another group of rats was exposed to room light but fitted with contact lenses that allowed the green spectrum wavelength to pass through their visual systems. A third group of rats was fitted with opaque contact lenses, which blocked the green light from entering their visual system.

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While the first two groups benefitted from exposure to green light showed more tolerance to thermal and tactile stimulus than the third group, which did not show any improvement after the experiment.

The results of the study were published in the February issue of the journal Pain.

Light therapy has earlier been useful for many medical conditions including depression. The study said that light therapy may have psychological effects arising from physiological changes such as increased opioid release from within the body, which affect pain response and perception. The study found no side effects of the light therapy and the beneficial effects lasted for four days after the rats’ last exposure to green LED.

The results of the study are preliminary and the authors will conduct a clinical trial using green LED in people with fibromyalgia, which includes a widespread pain of muscle and bones.