Like most living creatures on the planet, we are sensitive to the comings and goings of the sun. Over millennia, our bodies developed their own cycles, responsive to light and dark, called circadian rhythms. Because sunlight dictates much of these rhythms, we are affected by seasonal changes. But the prevalence of artificial light takes us out of sync with nature and with the seasons. And don’t get me started on changing the clocks twice a year. Few things have a more negative impact on my patients’ moods than daylight saving time manipulations.
Until the invention of the light bulb, we spent an average of twelve hours a night in the dark, depending on the season. Ever since we started to extend our day length with artificial lights, we have been getting less sleep than we need. This has repercussions for metabolism and weight maintenance. We are hardwired to store fat during the summer in order to prepare for food shortages in the winter. The longer light exposure warns our bodies that the famine is coming and that we’d best eat carbohydrates now or starve later.
Excess light at night suppresses melatonin release and basically tricks our brains into thinking it’s always August.
Sleeping in a dark room and avoiding any exposure to nighttime light is a crucial factor for getting good sleep and staying healthy. But this is not just about light bulbs. Just two hours of iPad use at maximum brightness is enough to suppress the normal nighttime release of melatonin, and two hours of computer use not only lowers melatonin secretion but also enhances cognitive performance and sustained attention. So I get why all my patients are telling me about their second wind at night when they get home and log on. The problem is, we don’t need a second wind. We need sleep.
If you must be in front of a glowing screen at night, at least consider using a program called f.lux that dims your computer screen depending on the time of day. There’s also the option of wearing blue-blocking sunglasses at night to filter out the spectrum of light thought to stimulate circadian receptors the most. (We know melatonin is particularly suppressed by sky-blue sunlight.) Blue blockers can significantly improve sleep quality, positive affect, and mood.
But growing research is backing up the advice I have been giving to my patients for years: No glowing screens at least one hour before sleep. Dim the lights and shut off your television. Do not bring your laptop to bed with you, and put down your iPhone. If you’re going to read, books or magazines are the way to go, not backlit iPads. Even electronic readers can shift your circadian rhythm signals to later hours, prolonging the time it takes to fall asleep.
What? No computers or TV at night? Whatever will I do? Try getting out of cyberspace and back into your body. Breathe. Stretch. Wind down and relax. Take a hot bath. Drink some herbal tea and just sit down for a spell. Listen to music. Meditate. Write in your journal, especially about all the things you have to be thankful for. Gratitude is good for your mood. Appreciate the darkness and the silence. As a prelude to sleep, try some inactivity, light some candles, and take some time to cultivate stillness. Most important, power down your devices and just be.
Julie Holland, MD, is a psychiatrist specializing in psychopharmacology, with a private practice in New York City. A former Assistant Clinical Professor of Psychiatry at the NYU School of Medicine, Dr. Holland is the author of Weekends at Bellevue: Nine Years on the Night Shift at the Psych ER (Bantam Books) and numerous other books and articles.