Seasonal Affective Disorder (SAD) FAQ Sheet

** See bottom of page for some educational videos

What is Seasonal Affective Disorder (SAD)?

Seasonal Affective Disorder (SAD), also known as "winter depression," not to be confused with "winter blues," is a mood disorder that's characterized by depressive symptoms during the winter months year after year. Some people also experience SAD during summer and spring, although this is less common. People who suffer from SAD may feel extremely tired starting fall, and then feel progressively depressed during winter. SAD usually goes away on its own when spring comes.

SAD patients may sleep too much, feel weak, or crave sweets and starchy foods. They may find it hard to concentrate or be irritable. Some people lose interest in what's going on around them and just sleep as much as possible to let the bleak days pass. There is also a potential risk of suicide in some patients suffering from the disorder. SAD is a debilitating form of depression, but it's easily treatable once diagnosed.

What are the symptoms of SAD?

SAD symptoms are similar to those of common depressive disorders; the only difference is that they occur seasonally, usually during fall and winter, and disappear when spring arrives. Diagnosis of SAD is more reliable if the cycle of symptoms has occurred for at least two consecutive years. The following are the common symptoms:

  • Depression

  • Hopelessness

  • Lack of interest in activities previously enjoyed

  • Fatigue and low energy

  • Longer sleeping time

  • Difficulty concentrating

  • Craving sweets and starchy foods

  • Overeating that may result in weight gain

  • Anxiety

  • Suicidal thoughts or feelings

SAD can also occur during summer or spring, although it's less common. The following are the symptoms of summer-onset seasonal affective disorder:

  • Irritability

  • Anxiety

  • Insomnia

  • Increased sex drive

  • Poor appetite

  • Weight loss

In very rare cases, people with SAD don't experience depression-like symptoms. Instead, they experience symptoms of mania or hypomania, a less intense form of mania, during summer or spring. This kind of disorder is sometimes called reverse SAD, and it's more common among people with bipolar disorder. The following are the symptoms:

  • Euphoria

  • Hyperactivity

  • Increased social interaction

  • Enthusiasm that's out of proportion to the situation

What causes SAD?

While the precise causes of SAD are not yet known, research links the disorder to people's circadian rhythm or "biological clock," and their primal need for light. How people function in everyday life is closely tied to the 24-hour cycle of light and dark and to the rhythm of seasons. When an individual is affected by SAD, he loses that synchronization with the environment, causing disturbances in his hormones and other bodily processes.

SAD was recognized as a clinical disorder around 1980 by psychiatrist Al Lewy and his colleagues at the National Institutes of Health (NIH). They discovered that light can control the production of melatonin, a hormone that signals the body to sleep when the eye picks up less light. Melatonin and other hormones regulate the body's biological clock. They control the body's temperature, immune system, stress response, and many other things.

Blood tests can measure the amount of melatonin in the body, allowing researchers to determine whether the biological clock is turned off. While the specific link between the biological clock and depression is not yet completely understood, it is known that people who suffer from SAD have body clocks that run much slower during winter. Lewy even compares the condition to having jet lag for five months. Another factor in the occurrence of SAD is serotonin, a neurotransmitter. According to the Society for Neuroscience, low levels of serotonin have been linked to depression.

How is SAD different from other mood disorders?

SAD is usually confused with "winter blues" or "winter blahs" but the two are different. People living in the northern latitudes commonly complain of having less energy, feeling down, and putting on weight during winter. These symptoms characterize winter blues, but they occur at a much greater degree in people with SAD. For instance, SAD patients may extend their sleep by as much as four or more hours each day. Women with SAD also report worsening premenstrual symptoms. Another thing that distinguishes SAD from winter blues is that it repeats year after year, with the patient going through the same cycle of depression, and normalcy.

SAD is also different from "holiday blues," which refers to sadness or depression during the holiday season. Holiday blues are caused by psychosocial factors such as decreased exercise, increased family obligations, isolation, expectations that one should feel happy during the holidays, and unresolved childhood conflicts related to the holidays. In contrast, SAD has a more biological and genetic origin, and is a subtype of a major depressive disorder.

How is SAD similar to other mood disorders?

SAD's symptoms are very similar with winter blues, but they occur at a much greater degree. It's much harder to cope with SAD than with winter blues, and there is even a potential risk of suicide among patients. The distinguishing characteristic of SAD is that it occurs yearly at about the same time, which is why diagnosis is more reliable if the patient has experienced symptoms for two consecutive years.

Who suffers from SAD?

SAD afflicts more women than men for reasons still unknown. Recent studies also suggest that SAD is more common in northern countries since winter days get shorter as you go farther north. Many experts believe that shorter days and long nights in winter contribute to the occurrence of SAD. In the United States, for example, less than two percent of Florida's population experiences SAD, while 9.7 percent of New Hampshire's population suffers from it, according to a study published in the Journal of the American Pharmacological Association.

Studies in Ontario, Canada show that two to three percent of the general population has the disorder. This means that up to 100,000 people in British Columbia may experience annual clinical depression during winter. In addition, studies indicate that another 15 percent of the population suffer from winter blues. In the United States the incidence of SAD is lower overall as generally winters are less severe in many parts of the country as they can be in Canada. Similarly countries like Finland the United Kingdom and Germany have higher incidences of SAD because of their characteristic weather patterns. In all, cases of SAD within the US are higher in the North East and North West and specifically around the Great Lakes region.

I think I have SAD. What should I do?

Depression can have disastrous effects on your life and the people around you. Consult your doctor immediately if you're depressed or if you think you have SAD. Your doctor can treat you, or he may refer you to a psychiatrist who handles SAD cases. You can also search the Internet for SAD and depression support groups near you. Other sources of help include: the local suicide hotline, local hospital emergency room, your mental health center, and even members of your local church.

How is SAD diagnosed?

Doctors may use the standard survey for SAD known as the Seasonal Pattern Assessment Questionnaire or SPAQ. The survey evaluates the impact of seasonal changes on your energy, social activity, sleeping habits, appetite, and weight. Doctors may also use other standard questionnaires for depression to determine if you're afflicted with SAD.

What is the treatment for SAD?

Studies show that SAD patients can improve through light therapy or phototherapy, which involves exposing the patient to bright, artificial light. Sixty to seventy percent of SAD patients show significant improvement when they sit under a special fluorescent light box for 30 minutes a day. offers a diverse line of therapy lamps as well as full spectrum lighting to enhance your general well-being.

What is light therapy?

Light therapy typically involves the use of a fluorescent light box to illuminate the patient. Patients may purchase a light box and place it in their homes. In most cases, patients are required to sit under 10,000 lux, where lux is a measurement of light intensity. This is much stronger than indoor light, which is usually less than 400 lux, but below the light intensity of a cloudy day, which is 3,000 lux. Natural sunlight on a sunny day though is even stronger: 50,000 lux or more.

Many patients show improvement by using the light box 30 minutes a day. Generally, patients who undergo light therapy are instructed to sit facing the light box upon waking up. Evening doses of light can also work for patients with scheduling conflicts.

How does light therapy work?

In light therapy, the extra light intensity stops the production of melatonin, causing your body to shift from night to day mode. This process is based on the theory that light has an effect on brain activity and body functions. Light therapy corrects the biological clock that regulates hormones, mood, and sleep patterns. According to other theories, neurotransmitters like dopamine and serotonin are imbalanced in SAD patients, and that these disturbances are corrected by light therapy along with medications. Some experts believe that SAD patients have less retinal light sensitivity in the winter that light therapy corrects. Still, other scientists believe that SAD has a genetic basis.

When should light therapy be prescribed?

The following are the circumstances that support light therapy prescription for SAD:

  • You are not severely suicidal.

  • You have medical reasons to avoid the use of antidepressants.

  • You have no history of significant negative reactions to light therapy.

  • You requested for the treatment to be done.

  • Your doctor deems that light therapy is the best treatment for you.

How do I get a light box?

Safe and portable light boxes are now commercially available in regions where SAD is prevalent. You may ask your doctor or contact your clinic for more information on light boxes and light therapy. In North America, the cost of a light box is usually between $200 and $400. It's not advisable to build your own light box because of the injuries that can occur, and you may have difficulties getting the correct "dose" of light. offers the top brands and lighting systems in our store and is here to help!

Does light therapy have any side effects?

Light box therapy is completely safe with only mild side effects. Some patients may experience eye strain, nausea, headaches, or feel a bit irritable when they first start using the light box, but these usually disappear with time. Light therapy has no long-term harmful effects, but experts recommend taking eye examinations first if you have diabetes or retinal disease.

How soon does light therapy work?

Most patients notice improvement in two to four days. In some cases, however, symptoms may not improve for several weeks. If symptoms do not improve or worsen after four to six weeks of light therapy, see your physician. You may require a change in treatment, or your physician may add other drugs to your therapy.

Are there any other treatments for SAD?

Seasonal Affective Disorder is very similar to depression, so antidepressant medications like selective serotonin reuptake inhibitors or SSRIs are effective in treating the disorder. If you have SAD, it's also advisable that you seek counseling since the psychological and emotional stress may be too severe. People who suffer from winter blues, on the other hand, may simply exercise or spend more time outdoors to improve their condition.

Don't let your life be ruined by SAD. There are many ways to feel better, so break through the depression, and seek out the help you need.

0.115, 0.095, 0.02/18,