Shining a light on seasonal affective disorder may bring relief to winter blues
Feeling a bit of a letdown after the celebrations and bright decorations of the holidays is natural. But if your post-holiday blues continue for weeks — or months — during the dreary winter, you may be suffering from seasonal affective disorder, also known as SAD.
SAD is a type of depression that usually recurs in the winter and subsides in the spring. Symptoms are the same as in other types of depression:
- Sadness, unhappiness or hopelessness
- Fatigue, decreased energy and increased sleep
- Increased appetite
- Difficulty concentrating
- Loss of interest in favorite activities
- Social withdrawal
“People who’re suffering from seasonal affective disorder may start eating a lot and craving chocolate. They feel tired, exhausted; they’re dragging themselves around,” says Prashant Gajwani, MD, associate professor of psychiatry and behavioral sciences at The University of Texas Health Science Center at Houston (UTHealth) Medical School.
Also called winter blues and cabin fever, the condition has been known for centuries. In Iceland, a short-days depression was even mentioned in medieval epics.
“SAD is seen mostly in areas where, during the winter months, the days become very short and access to sunlight is very limited,” Gajwani says. “I lived in Cleveland, Ohio, before coming to Houston. In Cleveland, the winters are terrible. The sun sets at 3 o’clock; it’s cloudy frequently. You can go through the whole winter without seeing the sun.”
At the end of the 20th century, a major discovery in the eye increased understanding of the physiological effects of this lack of sunlight. Scientists found that a small subset of ganglion cells in the retina — about 20,000 out of 150 million retinal cells — produces a light-sensitive pigment that they named melanopsin.
Setting the clock
These cells are not primarily involved in forming visual images. Instead, they receive light and send light information to a body clock (or biological clock) located deep in the brain, in the hypothalamus, to keep the clock synchronized with the daily 24-hour light-dark cycle, or circadian rhythm.
“These cells need bright light to elicit a response,” says Christophe Ribelayga, PhD, assistant professor of ophthalmology and visual sciences at UTHealth Medical School. “When the day is shorter in winter, the sunlight also is much weaker and dimmer. Then you start having problems of entrainment (synchronization) of the body’s clock and with all the physiological functions that are controlled by the clock, such as the sleep-wake cycle.” The sleep-wake cycle is related to alertness, and alertness is related to mood.
A misalignment between circadian rhythm and the body clock builds up over several weeks, so that eventually one will need to go to work when his body clock tells him to sleep, Ribelayga says.
“There’s a conflict between a body clock that is not in phase with the light-dark cycles and what the individual must do in his social or professional life. We think that in the long term, that generates enough conflict to cause depression,” he says.
A related mechanism involves the hormone melatonin, which is released at nighttime.
“We secrete melatonin when the sun goes down, so we can sleep,” Gajwani says. “When we see sunlight, we stop secretion of melatonin, so that we can wake up. When there’s not enough sunlight, we don’t stop the melatonin secretion in the body, and therefore, we are still sleepy, tired and exhausted.”
Another hormone implicated in SAD is serotonin, which is vital for mood and a decrease in its transmission is linked to depression, Ribelayga says.
“Scientists have noticed that people who have seasonal affective disorder have low levels of serotonin. People need an appropriate period of sunlight and good synchronization of the body clock to maintain normal levels of serotonin,” he says.
Development of SAD represents an abnormally strong response to seasonal light changes. The response varies with one’s vulnerability. Generally, the disorder develops between the ages of 18 and 30. Like other forms of depression, it is more common in women.
“Mental illnesses have a strong genetic component; they run in families,” Gajwani says. “If your mother had winter blues, there’s a chance that you might also have seasonal affective disorder.”
About 5 percent of the U.S. population, or nearly 16 million people, have SAD, according to former National Institute of Mental Health psychiatrist Norman Rosenthal, MD, who has been researching the disorder since the 1980s. He reports the prevalence at far northern latitudes, such as Norway, as high as 14 percent. The geographical influence is related to the extreme difference in the length of days — from the midnight sun in the summer to more than a month of total darkness in the winter — in the far north.
“You don’t have seasonal affective disorder in the tropics,” Ribelayga says. “You might feel blue during a week of cloudy days, but it takes three or four weeks of reduced light exposure to develop SAD.”
What to do
For people in Norway, Sweden or Alaska, a winter vacation in sunny Spain might be the perfect prescription for treating SAD.
A much less expensive and more practical treatment for most people is phototherapy, exposure to very bright light that mimics sunlight. Sixty to 80 percent of SAD sufferers benefit from phototherapy. Exposure to bright light early in the morning appears to be most effective.
Light boxes are widely available on the Web and in some drugstores and discount stores. Looking directly at the light box is not needed or recommended. What’s important is the background light intensity.
“You work under that light for 30 minutes or an hour,” says Gajwani, who used a light box in his office in Cleveland. “So the light is indirectly going into your eyes, and through your eyes, the message is communicated to your brain that, ‘Hey, I see sunlight.’”
Because melanopsin is sensitive to blue light, some scientists have theorized that blue light might be more effective against SAD than white light. But recent studies have shown that white light is just as effective. “It might be better not to use blue light,” Ribelayga recommends, because the very high energy of blue light carries a potential for damage to the eyes.
What not to do
The light box is not used for tanning, Gajwani emphasizes.
“Some people use tanning beds because it makes them feel good temporarily. But the American Academy of Dermatology has made strong statements against these tanning beds because of the increased risk of skin cancer,” he says. “Plus, they don’t have the same wavelength as light boxes. So although you feel warm and you tan, it does not treat your seasonal affective disorder at all.”
Excessive drinking is another maladaptive strategy some people use to cope with SAD. At far northern latitudes, SAD is thought to contribute to increased rates of alcoholism and suicide during winter months.
Recent research has shown a potential benefit from use of melatonin at bedtime to help synchronize the body clock and use of certain prescription antidepressants to increase serotonin levels.
“We use the synchronizing properties of melatonin to set the phase of the clock in blind people,” Ribelayga says. Taking one pill of melatonin each night before bed helps the body clock synchronize with nighttime, which might complement the effects of bright light in the morning for people with SAD. However, Ribelayga notes that melatonin’s effectiveness might be impaired because of its rapid clearance from the body, since it is flushed out in only two hours.
A new prescription drug Ramelteon, marketed as Rozerem, mimics the beneficial effects of melatonin and stays in the body for 12 hours. “It may be very useful for people who have trouble sleeping, who are desynchronized, and who have seasonal affective disorder,” Ribelayga says.
If using a light box alone is not effective or if symptoms are severe, one should see a doctor. For example, during the winter, a patient with bipolar disorder may be depressed and then, during the spring, have a manic episode, which is characterized by an abnormally and persistently elevated, expansive mood, racing thoughts and a decreased need for sleep. Proper diagnosis and treatment is important.
“The professional can assess what else may be going on,” Gajwani says. “Sometimes we have symptoms caused by several things, so you need a professional to guide and help you.”