Sunlight plays a key role in my life. Whenever it gets dark and gloomy, I feel down; during the sunny day, I feel optimistic and full of energy. These feelings are universal and deep-rooted for us. However, nowadays we live the majority of our lives with artificial light indoor, travel often between time zones. That has a great impact on how we feel and how we work.
The bright light therapy, or exposing yourself to light to feel better, is getting more and more popular. The Scandinavians get it from the state during the polar night, many are interested in it to fight the jet lag or dysthymia. How does it work? I present you the three basic facts about the therapy you must know:
1. Light exposure dictates your daily activity
Your circadian rhythm is a set of physical and mental changes that your body goes through a roughly 24-hour cycle. The “master clock” of your circadian rhythm is in your hypothalamus, called suprachiasmatic nuclei (SCN for short). Because we are diurnal animals, our top-notch performance is during a morning and late evening, while overwhelming sleepiness gets us in the middle of the night. The main point of bright light therapy will be to affect your circadian rhythm to better align with your daily life. Adjusting circadian rhythm helps you sleep better and improves your mood, energy levels, and general performance.
2. Why does the light matter so much
Light stimulates your retina, creating a neural signal to your hypothalamus along the retinohypothalamic tract. SCN decodes this signal and stimulates both nervous and endocrine systems. During the day, SCN activates reticular formation which forces the rest of your brain to stay alert, while stimulated endocrine glands secrete cortisol, crucial in keeping a high metabolic rate of the organism. When you are in the dark environment, SCN activates pineal gland to secrete melatonin, a sleep hormone, which induces sleep and lowers metabolic rate of the organism. This balance is crucial; that’s why you learn about a reduction of light stimuli before the sleep as a basic of sleep hygiene. Also, it’s the base idea of the bright light therapy improving your performance.
3. Your master circadian clock is most sensitive to light when you are asleep
Recent research has shown that humans’ master circadian clock responds relatively stronger to relatively smaller amounts of light during the night. You can get greater circadian shifting results from shorter periods of bright light therapy during the night. However, constant light shining brightly during night gets counterproductive when you want to get the rest that you’re missing in the first place.
That’s where this recent study comes in. It showed that millisecond flashes of light through subjects’ closed eyelids (while they were asleep) were enough to make use of the nighttime advantage for circadian shifting without affecting their sleep. This finding made nighttime bright light therapy a practical opportunity for busy people in today’s sleep-deprived, jet-lagged world. Another way around it is to schedule light stimulus gradually before desired waking time, to mimic natural dawn.
Bright light stimulus is a signal to activate our body both mentally and metabolic-wise. Planned timing of the light stimulation regulates circadian rhythms while the natural sources are disturbed, like when traveling between time zones or during polar night. A heightened metabolic rate is what you feel as an energy kick, while brain activation provides clear mind and the heightened mood. The bright light therapy — in particular at night — may help to keep the master circadian clock ticking normally.
Have you ever tried light therapy? What was the cause, what was the results? Share your experience with us in the comment section below!
The medical science liaison in Neuroon Open, Medical Doctor. I am interested in psychiatry, neuroscience, and epistemology. As a former biology-class teacher and a physician by profession, I try to explain complicated and non-trivial subjects of neuroscience and psychiatry in an easy-understandable fashion. I produce and play music in my free time.