Seasonal Affective Disorder

What is Seasonal Affective Disorder?

For millions of Americans with winter depression, or Seasonal Affective Disorder, sunlight streaming through the window after months of gray skies is more than a sign of spring. It means that the depression that has lingered during the dark winter months will also lift. People with the disorder may soon feel energetic again, perhaps inspired and involved.

In the fall and winter months, as the days grow shorter and there’s less sunlight, those susceptible to the syndrome feel their spirits sinking, the world shrinking. If you have Seasonal Affective Disorder (SAD), you may feel empty and forlorn. You may find it difficult to concentrate, or perhaps you’ll be unusually edgy and irritable. It’s common to lose interest in what’s going on around you and seek to shut out the bleak days by sleeping as much as possible. You may also try to escape feelings of loneliness and despair through food: Those captive to SAD typically overeat and crave sugary or starchy “comfort” foods when they are depressed.

This mood disorder generally sets in during late fall or early winter and lets up in spring. Seasonal Affective Disorder is a debilitating form of depression, but once detected, it’s easily treatable.

What are the symptoms?

The most common symptoms are the same ones that signal any depressive disorder. What distinguishes SAD from other types of depression is that symptoms appear seasonally, usually in autumn and winter, and disappear during sunnier times of the year. The diagnosis is firmer when the cycle has occurred for at least two consecutive years. The following are typical characteristics of SAD:

  • Low energy and fatigue
  • Lack of interest in previously enjoyed activities
  • Difficulty concentrating
  • Increased sleeping time
  • Overeating and possible weight gain
  • Craving for sweet and starchy foods
  • Anxiety
  • Suicidal feelings (in rare cases)

Less commonly, SAD can strike those who have bipolar disorder, also known as manic depression. For people with both illnesses, winter depression may change in the spring or summer to mild mania, or euphoria, known as hypomania.

Who is afflicted by SAD?

SAD strikes more women than men. Perhaps not surprisingly, it also affects more people in cold northern climates than their counterparts in the sun-drenched warmer latitudes of the globe. In Florida, for example, the disorder strikes less than 2 percent of the population, while 9.7 percent of people in the northern state of New Hampshire are afflicted by it, according to a study in the Journal of the American Pharmacological Association.

How is SAD diagnosed?

Doctors use the standard survey for SAD, a diagnostic tool also known as the Seasonal Pattern Assessment Questionnaire (SPAQ). The questionnaire assesses the impact of seasonal changes on your sleeping habits, social activity, mood, weight, appetite, and energy. Other standard surveys for depression can also help a doctor determine if you have SAD.

What causes SAD?

The precise reasons this seasonal interloper appears are not known. However, most of the research links it to our primal need for light and our body’s circadian rhythms, or so-called “biological clock.” “The quality of human performance is closely tied to the 24-hour cycle of light and dark and to the predictable rhythm of the seasons,” writes psychologist Peter Whybrow in his insightful book on depression, A Mood Apart. “And it is precisely this comfortable fit with our planetary environment that is lost in winter depression.”

SAD wasn’t recognized as a legitimate clinical disorder until around 1980, when psychiatrist Al Lewy and his colleagues at the National Institutes of Health first identified the illness. “We were studying a person who got depressed every winter, and [we] had just discovered that light could control the production of melatonin,” explains Lewy, who now is vice chair of the department of psychiatry at Oregon Health Sciences University. Melatonin is a hormone produced by the body that increases when the eye picks up less light, mainly during the dark hours, and signals the body to ready itself for sleep.

Melatonin and other hormones regulate the body’s circadian rhythms, or responses to the 24-hour cycle of night and day. They control sleep, body temperature, the ability to deal with stress, and the workings of the immune system, among other things, explains Lewy. A blood test can measure fluctuations in melatonin, allowing researchers to gauge whether a body’s “clock” is off. Although the specific link between circadian rhythms and depression is not understood, it is known that people with SAD have biological clocks that run much too slowly in winter. For them, explains Lewy, “It’s like having jet lag for five months.”

Also implicated in winter depression — but not understood — is the way the body processes the neurotransmitter serotonin. Low levels of this brain chemical have been linked to depression, according to the Society for Neuroscience.

In January of 2016, however, a survey of more than 34,000 U.S. adults found no evidence that levels of depressive symptoms vary by season. The study, published in Clinical Psychological Science, challenged the existence of SAD “as a legitimate psychiatric disorder.” However, the researchers conceded that it’s possible SAD does exist, but only in a very small subset of the population.

I think I’m in the minority of people who has SAD. How can I get relief?

Light is the first line of treatment for this malaise of darkness. Bright indoor lights won’t work. They are usually less than 500 lux (the unit of measurement for brightness). But a special fluorescent light box developed to fight winter depression can ward off symptoms of SAD. The boxes beam 10,000 lux of light filtered to prevent emission of damaging ultraviolet rays and are available at medical supply stores or through mail order.

The extra dose of light stops the production of melatonin, so your body shifts to day mode rather than night mode. Generally, those who use it are instructed to sit facing the light upon waking for up to two hours. For those with scheduling conflicts, evening doses of light can also work.

Not everyone can make use of light therapy, however. People who have had certain eye problems such as retinal disease may not be advised to undertake the therapy; these patients are referred to their ophthalmologists for an assessment. Similarly, those who take medications that cause heightened sensitivity to light may react poorly to the lamps. For those who aren’t good candidates for light therapy, antidepressants that affect serotonin production are a possible solution. Synthetic melatonin in pill form, an experimental treatment now under investigation, also works for some SAD sufferers, according to Dr. Lewy.

Whatever combination you and your doctor ultimately select, chances are good that it will help keep that internal darkness at bay.

Further Resources

National Mental Health Association 1021 Prince Street Alexandria, VA 22314 800-969-6642

The Society for Light Treatment and Biological Rhythms


M. K. Traffanstedt, S. Mehta, S. G. LoBello. Major Depression With Seasonal Variation: Is It a Valid Construct? Clinical Psychological Science, 2016; DOI: 10.1177/2167702615615867

Editors: Lam, Raymond W., Levitt, Anthony J. “Canadian Consensus Guidelines for the Treatment of Seasonal Affective Disorder: A Summary of the Report of the Canadian Consensus Group on SAD.”

“Seasonal Affective Disorder,” American Family Physician,

Jepson, Tracy L. et al, “Current Perspectives on the Management of Seasonal Affective Disorder,” J Am Pharm Assoc, Vol. 39(6): 822-829.

Partonen, Timo. “Seasonal affective disorder,” Lancet

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