At the end of October we set our clocks back an hour, watch the leaves drift to the ground and hunker down for the long march into winter. Most of us gripe about the cold, delight in the beauty of an overnight snowfall, read by the fire and daydream about warmer summer weather. But for some the short days and long dark nights of winter close around them like an icy prison, taking the joy from life and shrouding their days in oppressive gloom.

Winter depression or seasonal affective disorder (SAD) affects millions of Americans, especially those living in northern latitudes. The problem increases as the distance from the equator grows. The prevalence of SAD is estimated to be about 10 percent close to the Canadian border, around 6 percent in New York City but only 1 percent in the extreme south. Women are affected four times as often as men.

Symptoms of SAD include an increased need for sleep, irritability, a lower sex drive, a craving for carbohydrates and sweets, lethargy and an overall feeling of depression that shows up as a loss of interest and enjoyment in normal activities.

How can light affect mood so drastically? Scientists think that part of the answer can be found in our animal roots. Signals keyed to changes in the length of day affect the behavior of many animals, triggering increased intake of food, decreased sexual activity and increased need for sleep. Hibernation is one extreme of this tendency.

Humans don’t hibernate, but we do have a biological clock that controls our circadian rhythms. This internal clock governs our sleep/wake cycle and prompts the release of hormones that regulate body functions. The biological clock is set by external cues such as length of day.

Light enters through the eyes. Most of those light-borne signals are used to convey and interpret what we see. But part of the signal is diverted to a group of brain cells above the visual cortex known as the suprachiasmatic nucleus (SCN). From there signals are transmitted to the pineal gland, responsible for the release of the hormone melatonin. Melatonin governs body temperature and is believed to regulate the internal clock that controls the sleep/wake cycle. Normally released after nightfall, it makes us sleepy.

A number of studies show that persons with SAD release more melatonin in winter months than they do in summer. Persons without symptoms of SAD release melatonin at a fairly even rate, regardless of the season. Researchers think that those with SAD have a heightened sensitivity to seasonal light changes.

Let There Be Light
If light is at the root of the problem, it also offers a relatively simple solution to SAD. Light therapy is a widely used treatment and a number of controlled studies show that it is effective for a large number of patients. Researchers believe it works by decreasing the body’s production of melatonin and increasing the supply of serotonin, a neurotransmitter that enhances feelings of well-being. Other treatment options include antidepressant medications and cognitive behavioral therapy.

Light therapy involves the use of high intensity light that simulates sunlight delivered by specially constructed fluorescent light boxes or light visors worn on the head like a cap.

Light boxes deliver high intensity light, up to 10,000 lux, and are typically used for a half hour to an hour daily. Patients sit in front of the light box and can read or work.

Timing of light therapy seems to be important. A recent study conducted at Columbia Presbyterian Medical Center found that those who received light therapy in the morning were twice as likely to recover from SAD as those who had light therapy in the evening.

Other studies show that dawn simulation is even more effective than bright light. Dawn simulation involves exposure to white light that gradually increases in brightness, peaking at 250 lux after 90 minutes, while the patient is sleeping.

Researchers at the University of Washington in Seattle found that dawn simulation was more effective than a half hour of bright light in alleviating symptoms of SAD. Dawn simulation offers the advantage of being delivered in sleeping hours and requires little effort or scheduling on the part of the patient.

Side effects of light therapy include eyestrain, headaches, irritability and insomnia. Excessive exposure may cause skin problems.

When light therapy is used it should be given to properly diagnosed patients and used under a physician’s supervision. It should not be used by patients who are psychotic or suicidal.

Light therapy may take anywhere from a few days to a few weeks to be effective. For patients who aren’t helped by light therapy, other options are available.

One small study found that patients treated with cognitive behavioral therapy delivered in group sessions fared as well as those treated with light therapy. Patients treated with a combination of both light and cognitive behavioral therapy fared even better.

The cognitive therapy, in 12 group sessions lasting 90 minutes each, focused on winter coping strategies and addressed the role environmental changes play in the development of symptoms.

Physicians sometimes prescribe antidepressants, especially the SSRIs (selective serotonin reuptake inhibitors) to treat SAD. The University of British Columbia is currently conducting a study comparing the effectiveness of SSRIs with light therapy. SSRIs have fewer serious side effects than older antidepressants but can cause weight loss, changes in sexual functioning, agitation, insomnia, headaches and dizziness.

As spring approaches and the days begin to lengthen, symptoms of SAD begin to fade, eventually paling to a dim memory in the bright light of summer.

The fact that SAD disappears in the summer doesn’t mean it should be ignored, however. Treatment options are available that have brought relief to many patients. Anyone with symptoms of SAD should make an appointment with a physician to discuss her symptoms and an appropriate treatment plan.

If the first approach isn’t effective, try another option. Persons with SAD need to act to reclaim the winter and make it a productive and fulfilling season.

REFERENCES:
Melissa Abramovitz, “A SAD State of Mind,” Current Health 2, January 2001.
Evie Bentely, “Seasonal Affective Disorder,” Psychology Review, September 1999.
John M. Eagles, “SAD - Help Arrives with the Dawn?” The Lancet, December 22, 2001.
“How To Recognize when Winter Gloom Becomes an Illness,” Pulse, January 7, 2002.
A.J. Lewy, “Bright Morning Light Reduces Depressive Symptoms in Seasonal Affective Disorder,” The Western Journal of Medicine, November 1999.
“Seasonal Affective Disorder,” American Family Physician, March 1, 2001.
“Seasonal Affective Disorder Has Biological Roots,” Pain and Central Nervous System Week, January 7, 2002.
Leo Sher, “Genetics of Seasonal Affective Disorder,” The Lancet, March 9, 2002.
Carl Sherman, “CBT Works Well for Seasonal Affective Disorder,” Clinical Psychiatry News, February 2002.
Michael Terman, “Internal Night,” Archives of General Psychiatry, December 2001.
Thomas Wehr et al, “A Circadian Signal of Change of Season in Patients with Seasonal Affective Disorder,” Archives of General Psychiatry, December 2001.