Seasonal Depression (Seasonal Affective Disorder)

Last Editorial Review: 7/22/2012

Do the bleak winter months get you down more than you think they should? Maybe you have seasonal depression, also known as seasonal affective disorder or SAD. Seasonal depression is a mood disorder that happens every year at the same time. A rare form of seasonal depression, known as "summer depression," begins in late spring or early summer and ends in fall. But in general, seasonal affective disorder starts in fall or winter and ends in spring or early summer.

What Causes Seasonal Affective Disorder?

There are two seasonal patterns with SAD. One starts in the fall and continues through the winter, and the other starts in late spring or early summer. The fall-onset type of SAD, often referred to as "winter depression," is better known and easier to recognize -- and we know more about it than we know about its counterpart.

Hormones manufactured deep in the brain automatically trigger attitudinal changes at certain times of year. Experts believe that SAD is related to these hormonal changes. One theory is that reduced sunlight during fall and winter leads to reduced production of serotonin in the the brain. Serotonin is a neurotransmitter that has a soothing, calming effect. The result of there not being enough serotonin is feelings of depression along with symptoms of fatigue, carbohydrate craving, and weight gain.

Because foods high in carbohydrates (chips, pretzels, cookies) boost serotonin, it is thought that they have a calming, soothing affect on the body and mind.

SAD usually starts in young adulthood and is more common in females than in males. Some people with SAD experience very mild symptoms and feel out of sorts or irritable. Others have debilitating symptoms that interfere with relationships and productivity.

Because the lack of enough daylight during wintertime is related to SAD, it is seldom found in countries within 30 degrees of the equator, where there is plenty of sunshine year round.

What Are the Symptoms of SAD During Winter?

People with SAD have many of the normal signs of depression, including:

  • Decreased levels of energy
  • Difficulty concentrating
  • Fatigue
  • Increase in appetite
  • Increased desire to be alone
  • Increased need for sleep
  • Weight gain

What Are the Signs of SAD During Summer?

Symptoms of summer SAD include:

How Is Seasonal Affective Disorder Diagnosed?

It is very important that you do not diagnose yourself with seasonal affective disorder. If you have symptoms of depression, see your doctor for a thorough assessment. Sometimes, physical problems can cause depression. But other times, symptoms of seasonal depression are part of a more complex psychiatric problem. A health professional should be the one to determine your level of depression and recommend the right form of treatment.

How Is Seasonal Depression Treated?

There are different treatments for seasonal depression, depending on the severity of the symptoms. Also, if you have another type of depression or bipolar disorder, the treatment may be different. Many doctors recommend that patients with SAD try to get outside early in the morning to increase their exposure to natural light. If this is impossible because of the dark winter months, antidepressant medications and/or light therapy (phototherapy) may help.

What Is Light Therapy for SAD?

Light therapy for SAD uses a full-spectrum bright light that is shined indirectly into your eyes. When you use light therapy, you sit about 2 feet away from a bright light -- about 20 times brighter than normal room lighting. The therapy starts with one 10- to 15-minute session per day. Then the times increase to 30 to 45 minutes a day, depending on your response. It is important not to look directly at the light source of any light box for extended periods in order to minimize the risk of damage to your eyes.

Some people with SAD recover within days using light therapy. Others take much longer. If the SAD symptoms are not resolved, the prescribing doctor may increase the light therapy sessions to twice daily. Those who respond to light therapy are encouraged to continue until they can be out in the sunshine again in the springtime.

Does Light Therapy Work for Seasonal Depression?

Some researchers link seasonal depression to the natural hormone melatonin, which causes drowsiness. When light strikes the human retina, a process in the body decreases the secretion of melatonin. Light modifies the amount of melatonin in the human nervous system and boosts serotonin in the brain. So light therapy has an antidepressant effect.

Experts now believe that light therapy may be an effective treatment for people who have eating disorders, insomnia, and major depression (unrelated to SAD). Researchers have found that when depressed patients without SAD take antidepressants and use light therapy, there is an added benefit of increased energy and improved mood.

Can I Prevent Seasonal Affective Disorder?

If you have been diagnosed with seasonal affective disorder, here are some things you can do to help prevent it from coming back:

  • Try to spend some amount of time outside every day, even when it's very cloudy. The effects of daylight are still beneficial.
  • Begin using a light box when fall starts, even before you feel the effects of winter SAD.
  • Eat a well-balanced diet, including sufficient amounts of vitamins and minerals as recommended by the FDA. This will help you have more energy even if your body is craving starchy and sweet foods.
  • Try exercising for 30 minutes a day, three times a week.
  • Stay involved with your social circle and regular activities. Social support is extremely important for those with mood disorders, especially during winter months.

When Should I Call my Doctor About Seasonal Depression?

If you experience feelings of depression, fatigue, and irritability that come at the same time each year and appear to be seasonal in nature, you may have a form of SAD. Talk openly with your doctor about your feelings. Follow the doctor's recommendations for lifestyle changes and/or treatment if you have SAD.

If your doctor recommends light therapy, ask if the practice provides light boxes for patients with SAD. You can also rent or purchase a light box, but they are expensive and health insurance companies do not usually cover them. While side effects are minimal with light therapy, be cautious if you have sensitive skin or a history of bipolar disorder.

WebMD Medical Reference


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American Academy of Family Physicians: "Seasonal Affective Disorder."

National Institute of Mental Health: "What Is Depression?"

American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders: DSM-IV-TR, American Psychiatric Pub, 2000.

Fieve, R, MD. Bipolar II, Rodale Books, 2006.

National Institute of Mental Health: Science Update: "Properly Timed Light, Melatonin Lift Winter Depression by Syncing Rhythms."

Reviewed by Joseph Goldberg, MD on July 22, 2012

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