Migraines are thought to be caused by abnormal brain activity temporarily affecting nerve signals, chemicals and blood vessels in the brain. It's unclear what causes this change in brain activity, but genetics may play a part in making someone more inclined to experience migraines, often as a result of a specific trigger. There are many potential migraine triggers; hormonal, emotional, physical, dietary, environmental and medicinal.

The most common migraine symptom, a throbbing pain on one side of the head, can be accompanied by other unpleasant symptoms, including nausea and vomiting, increased sensitivity to light or sound, sweating, abdominal pain and diarrhoea.

Classified as a disabling illness that causes 25 million work and school days to be lost in the UK each year, migraine sufferers are long overdue a drug-free option for relief. After years of relying on painkillers such as paracetamol and ibuprofen, triptans that cause the blood vessels around the brain to narrow (reversing the widening of blood vessels that's believed to be part of the migraine process), and anti-emetics to relieve nausea, recent research into green light therapy has been welcomed with open arms.

While bright light typically worsens the splitting headaches that affect nearly 15% of the world's population, including around 10 million people in the UK, Harvard Medical School researchers found, in a 2016 study, that exposing migraine sufferers to a narrow band of green light significantly reduces light sensitivity and, intriguingly, can actually reduce headache severity by calming the brain, according to the study's author, Rami Burstein, PhD.

Humans can see green better than any other colour. The retina in a human eye can detect light between wavelengths of 400 and 700 nm, a range that we know as the visible spectrum. Each of the three additive primary colours that we can perceive corresponds to a different wavelength, with blue at the lowest wavelength (400 nm) and red at the highest (700 nm). Green resides in the middle of the spectrum at around 555 nm, where our perception is at its best. Because of this, it is believed that the colour green places a lot less strain on our visual system than other colours, allowing our nervous system to relax when bathed in its hue. This soothing quality may be one of the reasons it is often prevalent in places such as hospitals, schools and workplaces.

During a 2020 pilot study by the University of Arizona Health Sciences, participants were exposed to white light for one to two hours a day for ten weeks. After a two-week break, they were then exposed to green light for the same length of time daily over the same duration. During the study, they tracked the frequency and intensity of headaches. In addition, they completed regular questionnaires regarding health, comfort, and happiness factors such as their ability to fall and stay asleep or perform work.

Using a scale of 0 to 10, patients indicated that green light exposure resulted in a 60% reduction in pain, from 8 to 3.2. Green light therapy also reduced the duration of headaches and improved participants' ability to fall and stay asleep, perform chores, exercise, and work.

Lead author of the study and director of the Chronic Pain Management Clinic at the university, Dr. Mohab Ibrahim, says, "This is the first clinical study to evaluate green light exposure as a potential preventive therapy for patients with migraine. As a physician, this is really exciting. Now I have another tool in my toolbox to treat one of the most difficult neurological conditions—migraine." Although the research seems promising, the scientists involved describe their study as a "proof-of-concept" investigation and acknowledge that the small number of participants was a limitation, noting that they are planning a more extensive clinical study to demonstrate its effectiveness definitively.

Note: If you suffer from migraines, please discuss available treatments and therapies with your doctor. Information in this blog post is not intended as a substitute for medical advice. The Serious Readers Light & Sight blog provides a carefully curated selection of the latest light and sight news. If you require further information on this topic, please visit the article sources linked below.

Sources:

1. Harvard.
2. OUP.
3. HealthLine.
4. Pub MED.
5. UAHS Arizona.
6. Science Daily.
7. Very Well Health.
8. NHS.
9. CNN.