Seasonal Affective Disorder

By Wendy Innes. May 7th 2016

Seasonal affective disorder (SAD) is a type of depression that shows up in relation to the seasons, primarily winter, which is how it has come to be known as the "winter blues." The onset is usually felt at the same time each year, causing many people to assume that the "the winter blues" is not an actual medical condition. But it is, and that medical condition is seasonal affective disorder. There is a rare form of SAD that affects people in late spring and lasts over the summer, disappearing in the fall.

Like other forms of depression, SAD tends to affect more women than men. It usually affects women in their 20s, 30s and 40s, but it is possible for it to affect adolescents as well. Seasonal affective disorder affects between 4-and-6 percent of the American population, while 10 to 20 percent of the population suffers from a more mild form of the winter blues.


The exact cause of seasonal affective disorder is not known. Seasonal affective disorder is more common at higher latitudes. So the farther north a person goes, the higher the risk that he or she will begin to feel the effects of SAD. It is for this reason that experts believe that sunlight plays a large role in SAD, though there are two different schools of thought as to how it all works.

  • The first theory is that decreased exposure to sunlight causes the body's internal clock to slow down.  This internal clock regulates sleep, mood and hormone levels.
  • The other theory is that neurotransmitters, the chemical messengers in the brain, are altered in people who have SAD and that exposure to light may help rebalance these chemicals.

No matter the cause, there is a definite link between available daylight and seasonal affective disorder.


Many of the symptoms of seasonal affective disorder are the same as those associated with other forms of depression:

  • Afternoon slumps with decreased energy
  • Problems concentrating
  • Carbohydrate cravings
  • Decreased interest in work and other activities
  • Increased appetite
  • Weight gain
  • Sleepiness during the day
  • Increased sleeping at night
  • Lack of energy
  • Slow, lethargic movements
  • Social withdrawal

Summertime SAD has slightly different symptoms:

  • Weight loss
  • Decreased appetite
  • Insomnia


There are several treatment options for seasonal affective disorder. Talk therapy can be helpful and anti-depressant medications are used as well, but only as a last resort. The most effective form of treatment for SAD is light therapy.

Light therapy uses light that mimics very bright natural daylight. It is thought that during the wintertime the body's levels of certain chemicals that regulate mood and sleep can become imbalanced because these chemicals are regulated by daylight.

The lights used emit at least 10,000 lux, which is how the output of these lights is measured. Tanning beds emit light at these levels as well, but the difference is that there is no UV exposure with light therapy, unlike tanning beds. Sometimes these lights are a soft, blue color or they are bright white.

Most experts agree that the best time to use light therapy is early in the day, preferably first thing in the morning. Using light therapy too late in the day can lead to insomnia. Some of the more complex lights have timers and functions that mimic sunrise. Often people with SAD find it very difficult to wake up first thing in the morning, especially if they have to get up very early, so one of the lights that mimics sunrise would be ideal for them. These lights are also useful for treating sleep inertia as well. Occasionally, people who use light therapy experience eye strain, fatigue, insomnia and headaches.

With treatment, the prognosis for SAD is very good, although in minor cases the symptoms resolve themselves in the spring. Typically people find relief in 2-to-4 days and symptoms resolve within 2-to-4 weeks with light therapy.

Warning Signs

Every form of depression shares similar warning signs and suicide is always a concern. People displaying any of the following signs may require medical attention or immediate help from a professional or specialist:

  • Constantly discussing death
  • Taking unnecessary risks that could lead to serious injury or death
  • Losing interest in things that were once important to them
  • Making comments about being helpless, hopeless or worthless
  • Putting affairs in order, such as completing a will
  • Saying things about how much better the world would be without them
  • Sudden change in behavior from being very sad to very happy or very calm
  • Talking about suicide
  • Saying goodbye to friends and family

Seasonal affective disorder can certainly disrupt someone's life, but there is hope. With proper treatment and professional help, those with SAD can find themselves living their lives with everything back on track in no time.


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