In 2019, a study was published showing that bright light therapy helped army veterans suffering from chronic back pain to improve sleep, symptoms of post-traumatic stress disorder as well as the pain itself.
Results are clear: it worked
“Noting that people experiencing sleep disturbance are at greater risk of developing chronic pain and that improving sleep reduces pain and pain sensitivity, we proposed that a treatment that improves sleep and mood—morning bright light treatment—may reduce pain intensity among people with chronic low back pain,” the authors explain. And they continue with results.
“Morning bright light treatment led to reduced pain intensity, pain behaviour, thermal pain threshold sensitivity, post-traumatic stress disorder symptoms, and improved sleep quality.
“Those who undergo morning bright light treatment may show improvements in pain, pain sensitivity, and sleep. Advances in circadian timing may be one mechanism by which morning bright light reduces pain. Morning bright light treatment should be further explored as an innovative treatment for chronic pain conditions.”Burgess et al. (2019). An Open Trial of Morning Bright Light Treatment Among US Military Veterans with Chronic Low Back Pain: A Pilot Study. Pain Medicine, Volume 20, Issue 4, April 2019, Pages 770–778.
Sleep, pain and traumatic memories improved
First, the study again demonstrates that bright light therapy helps with sleep problems. Those were significantly reduced and sleep quality improved (medium effect sizes: d=0.4).
Second, the pain was alleviated. The effect was much smaller (d=0.26, meaning only a few percent of the pain intensity scales), but statistically significant. Unfortunately, there was no control group, so we can hardly guess whether it was due to placebo effect or the light really helped. Given the small effect size, we should avoid premature optimism and rather consider the pain reduction as the secondary benefit of the overall improvement.
Third, the pain improvement correlated with advanced sleep pattern (quite strongly: r=.55). This means that it really was the light changing the brain daily rhythm which affected the pain rather than placebo effect. Also, it suggests that it is important to use the light in the morning for pain. Nevertheless, it still does not create a solid ground for stating that light therapy may directly affect pain.
Fourth, score of post-traumatic disorder improved, while score for depression and anxiety did not. This is, however, not unexpected. Better result in scale of post-traumatic disorder is natural, because PTSD also includes sleep problems. Differences in anxiety and depression were not the aim of the study and the participants were not initially depressed or anxious – therefore, there was not much to improve.
Sleep was improved by bright light therapy in military veterans suffering from pain and post-traumatic stress disorder. The results also suggest a mild alleviation of chronic pain, but that may be the secondary effect of better sleep.