Migraine sufferers frequently avoid light and seek respite in darkness. A new study led by Beth Israel Deaconess Medical Center (BIDMC) researchers has discovered a previously unknown link between light-sensitive nerve cells in the eye and brain centers that control mood and a variety of physical parameters like heart rate, shortness of breath, fatigue, congestion, and nausea.
The findings were published online in Proceedings of the National Academy of Sciences, and they explain how light can cause negative emotions and unpleasant physical sensations that are common in migraine sufferers.
A migraine is a headache that usually affects one side of the head and causes extreme throbbing pain or a pulsing sensation. It’s commonly accompanied by nausea, vomiting, and excessive light and sound sensitivity.
“While studying the effects of color on headache intensity, we found that some patients reported finding light uncomfortable even when it didn’t make their headaches worse,” said lead author Rami Burstein, Ph.D., Vice Chairman of research in the Department of Anesthesia, Critical Care and Pain Medicine at BIDMC and professor of anesthesia Harvard Medical School.
“We found that exposure to different colors of light could make patients experiencing a migraine feel irritable, angry, nervous, depressed, and anxious. These patients also reported feeling physical discomfort, including tightness in the chest or throat, shortness of breath, light-headedness, and nausea.”
A warning sensation known as an aura arises before or with the headache for some people. Visual disturbances, such as flashes of light or blind patches, or other disturbances, such as tingling on one side of the face, arm, or leg, and difficulty speaking, can all be signs of an aura.
We now have a physical explanation of why migraine patients have negative reactions to light. And now we are working on ways to use this information in hopes that soon migraine sufferers will be able to avoid not only the pain but also the negative emotions and physical discomfort that light creates for them.Rami Burstein
Some migraines can be prevented and made less unpleasant with the use of medication. The correct medications, in combination with self-help treatments and lifestyle adjustments, may be beneficial.
Burstein and colleagues asked 81 persons who had headaches on a regular basis and 17 people who had never had a migraine to describe what they saw under different colored lights.
The effects of light and color were examined three times: once on those who had never had a migraine before, and twice on migraine patients, once during an episode and once between attacks. All colors of light elicited unpleasant physiological sensations in migraine sufferers during and between attacks, according to the study.
When migraine sufferers were exposed to all light hues except green, they reported intense emotional responses such as rage, uneasiness, hopelessness, sadness, depression, anxiety, and dread.
Participants who did not have migraines did not have a strong physiological response to any color of light, yet all colors of light elicited pleasant emotions.
“These findings explained accounts from earlier work from blind migraine sufferers in a previous study,” said Burstein.
“We had noticed that light exacerbated headache intensity in participants who perceive light but have no sight as a result of loss of rods and cones, but not in those who lack light perception because of optic nerve degeneration. This suggested the nerves relaying signals from the eye to the brain played a critical role in the discomfort associated with migraine.”
Rodrigo Noseda, Ph.D., a researcher at BIDMC and an assistant professor of anesthesia at Harvard Medical School, identified previously unknown connections between nerve cells in the retina, the back of the eye where light is detected, and neurons extending into regions of the brain that regulate physiological, autonomic, endocrine, and emotional responses to changes in the external environment, in a pre-clinical experiment with albino rats.
“We now have a physical explanation of why migraine patients have negative reactions to light,” said Burstein. “And now we are working on ways to use this information in hopes that soon migraine sufferers will be able to avoid not only the pain but also the negative emotions and physical discomfort that light creates for them.”
Burstein and colleagues released research last year that found that the intensity of migraine headaches increases with blue, red, amber, and white lights but lowers with a specific wavelength of green light.
They discovered that green light activates retinal and brain neurons less than blue, red, amber, and white light, and hence is less likely to produce the physiological, autonomic, endocrine, and emotional responses that migraine sufferers commonly report.