Winter. The days are fleeting, and darkness is the rule. With fewer daylight hours, people often get to the office before the sun rises and leave after it sets. In some parts of the country, people wage a daily battle against the bone-chilling cold, and in others they are greeted most mornings by incessant rains. For some the winter holidays offer no relief. And even if the holidays weren't a harrowing experience for you, by now there are no gift-laden holiday mornings or reverie-filled nights to look forward to.

It's not surprising that, according to the National Mental Health Association, as many as six in every 100 Americans are afflicted with Seasonal Affective Disorder (or SAD, also known as winter depression), and 25% more report feeling significantly worse in the wintertime.

Dr. Raymond Lam, a psychiatrist, professor, and researcher in the field of mood disorders, has been studying SAD since it was first recognized as a disorder in the mid 1980s. He describes SAD as a psychological disorder akin to depression — in fact, Dr. Lam says, SAD is considered by many to be a subtype of clinical depression. The symptoms are, for the most part, very similar: low mood, crying spells, loss of interest in daily activities, an inability to concentrate. But then there are also some symptoms that are particular to SAD; severe fatigue, for example, and intense cravings for carbohydrates and starches. People suffering from SAD also tend to oversleep in the winter — three or four hours more than they normally would.

In the Dark

Why is it that the wintertime brings on these awful feelings and debilitating behaviors? According to Dr. Lam, it's not just the stress of the holidays, nor is it the cold weather. The key is light.

For years, scientists knew that melatonin was a key player in the seasonal patterns of animal behavior; geese fly south in the winter and bears hibernate because of — at least partially — high melatonin levels in the body. And scientists knew that light affected melatonin production. Because melatonin is only produced in the absence of light (at night), longer summer days meant less melatonin being produced. Dr. Lam related a common experiment done on Canada Geese, where "you can fool a Canada Goose into thinking its summertime in the winter just by turning on a room light because it shuts down its melatonin production, making the goose think that it's experiencing the shorter nights of summer — the goose will fly in the opposite direction than it would in the wintertime."

But it wasn't until the mid 1980s, during what Dr. Lam likens to a "perfect storm" of melatonin-based research, that researchers began to realize that light affects melatonin in humans much the same as it does in animals — it just took a much stronger light. And that's when scientists understood that depression really could be affected by the seasons, and by changing light.

In the doldrums of the cold season, when days are short and nights are long, we want to sleep late and get up when the sun comes up — that's our natural physical response to low light. But we can't; for most of us our days start at 8 a.m. and go until 5 or 6 p.m. whether we like it or not. And for some people, this causes severe depression. For these people, it's as though their natural tendency towards seasonal-behavior pattern changes is being stymied, and so instead they experience severe seasonal mood patterns.

Dr. Lam highlights two main theories that might explain the connection between light and depression. One, he says, may be related to a de-synchronization of our biological clock. Some people are surprised to discover that the biological clock isn't simply a metaphor; it's an actual, discrete, locatable part of the brain: the suprachiasmatic nucleus. The clock, Lam says, "is regulated by light acting through the eyes, and allows us to keep these daily 24-hour rhythms so that we function in a normal way." People who experience SAD may "become out of synch with the changing levels of light from winter to summer, as though experiencing a form of jet lag." Similar to how your body may have trouble adjusting to changing time zones, someone suffering from SAD can't adjust to the changes in light.

The second theory may be even more startling. Some scientists are starting to think that light can affect the behavior of neurotransmitters like serotonin and dopamine — the very same neurotransmitters commonly discussed in relation to depression and affected by antidepressant medication. The biological clock, says Dr. Lam, not only controls our sleep/wake cycle, but it also regulates the release of hormones and neurotransmitters. For people with SAD, lack of enough light may lead to an inadequate amount of dopamine and serotonin.

Shedding Some Light

Because of these theories, there is currently an explosion in research money and time committed to studying light therapy. Sitting in front of a light lamp may not only cure seasonal depression; it may eventually be a replacement for pills when it comes to the treatment of clinical depression. In fact, to find out, Dr. Lam and his team have just begun the largest study to date of light-therapy treatment for clinical depression. Funded by the Canadian Institutes of Health Research, this three-year study will compare light therapy, negative ion therapy, and antidepressant medications head-to-head to see how well each treatment can treat non-seasonal depression.

Light therapy isn't exactly new, but it does seem novel. It's hard to wrap your head around the fact that sitting in front of a glorified desk lamp may cure serious clinical depression. Nevertheless, according to Dr. Lam and countless other experts — as well as numerous clinical studies — it does work. "The light has to be bright enough to have a biological effect, which is much brighter than ordinary room light," Dr. Lam says. The standard for therapeutic light boxes is a 10,000 lux fluorescent light. Dr. Lam suggests that most people only need about a half hour of use daily, preferably early in the morning. "You have to be awake — the effect is through the eyes," says Dr, Lam, "but you can be eating breakfast or reading or anything else while getting light exposure." It usually takes a week or two for positive effects to occur, but once they do, they are substantial: two thirds of people with SAD get significant relief from their symptoms using this treatment. That's just as good as medication; Dr. Lam was one of the leads on a head-to-head comparison of light therapy and Prozac in treating SAD that found light therapy to be just as effective as the medication.

Light therapy is a simple treatment, and it has become more and more common. Light boxes are now widely available in drug stores and online. They only cost about $100-200 and are sometimes even covered by insurance. Unfortunately, light boxes are currently not being regulated by the federal agencies. When purchasing a light box, Dr. Lam recommends choosing one that:

  • Has been used in clinical trials and found to be effective.
  • Is manufactured by firms with a track record.
  • Has taken care of basic safety issues like electrical safety.

For more information on light boxes, visit the University of British Columbia's SAD Information website at

Changing the Season

It's useful to "think of seasonality as a dimension," says Dr. Lam. Then you start to see it in other conditions as well. Studies show, for example, that women with bulimia tend to have worsened eating and mood symptoms in the winter. It also helps explain why so many people experience worsened moods during the winter. Dr. Lam notes that although many people feel worse in the wintertime, if you start to feel as though your ability to function is disrupted because of depression-like feelings, you may have SAD and should seek out professional help — "it can," he says "get to the point where people have thoughts of guilt, self-blame, hopelessness, down to thoughts of suicide."

It's hard to say why certain people are more prone to developing SAD than others. Most of the theories suggest genetic propensity — just as certain people have more trouble with jet lag than others or a higher susceptibility to psychiatric disorders, it seems as though some people are just born more likely to become depressed in the wintertime. There is only one environmental factor, and that's latitude: the farther north you go, the more common SAD is. Latitude, of course, indicates that length of day (and therefore amount of sunlight) is the key component to risk of SAD — days get shorter the farther you move away from the equator. It's no surprise that prevalence of SAD has been shown to be higher than average in Canada, Northern Europe, and (in the Southern Hemisphere) Southern Australia.

Luckily, with light therapy, SAD may be one of the most treatable psychological disorders out there. Now, Dr. Lam and like-minded experts are starting to work with clinical practitioners to get this safe and effective treatment into the hands of patients worldwide, in order to make the winter a brighter, happier season.

To learn more about Seasonal Affective Disorder, visit the Healthline learning center or the UCB's SAD Information website.