Light Therapy: Not Just for the Blahs
It's the stuff of poems and songs. It's built into legends and verse. And as anyone who has stubbed their toe on a dark morning will tell you, it's the first thing they reach for when they catch their breath: "Where's the %$&! light?!" Yet, light does far more than inspire and illuminate; scientists and doctors are discovering that it's a powerful tool in the process of healing.
Shedding light on depression
Most compelling, particularly during the long, dreary Canadian winter, is the work being done with light therapy to treat seasonal affective disorder (SAD), a form of depression that affects up to three percent of Canadians, with another 15 percent suffering from milder "winter blues."
"There's a lot of interest these days in light and circadian rhythm," says Dr. Raymond Lam, the head of the University of British Columbia's Mood Disorders Centre. "People can understand how light affects them in a very direct way."
The idea is pretty simple. Like every other mammal on the planet, humans have developed a roughly 24-hour body clock -- the circadian rhythm -- governed by a biological clock in the brain that controls various hormones, including melatonin, a.k.a. the sleep hormone. The brain clock responds to the light-dark cycle. During dark hours, our bodies repair DNA and replenish melatonin.
The first light at dawn helps reset our circadian clock, so that by dusk, melatonin is released in anticipation of rest. Without the right balance of daylight and dark, however, our body clocks don't ticktock in time. As the circadian rhythm is thrown out of balance, the release of melatonin and "feel-good" neurotransmitters that govern mood is negatively affected. For some, that leads to seasonal depression.
But not just any light at any time of the day will help correct this problem. "It's the timing of the light that's important rather than how much you get during the day," says Lam. "For those with SAD, the optimal time is early morning, around 7 a.m. Your biological clock is more sensitive to light at that time. Light during the middle of the day has no effect on the biological clock."
What's more, in the past 10 years researchers have discovered that it isn't medium-wavelength yellow light, needed for optimal vision, that has the power to shift circadian rhythm; it's shorter-wave visible blue light (the light waves that make the sky appear blue). "If you have symptoms of depression, you should check with your family doctor before using light therapy," adds Lam.