Many people have difficulty dealing with the darker, shorter days of winter. They struggle to get out of bed in the morning, have less energy, feel down, and gain weight. For people with ]]>seasonal affective disorder (SAD)]]> , these changes are severe enough to cause significant problems in their everyday lives. But what exactly is SAD? How does it differ from the "winter blues" and normal sadness? And how can it be treated?

What Is Seasonal Affective Disorder?

SAD is a type of ]]>depression]]> that occurs due to a lack of exposure to light during the winter. It usually begins in the fall (October or November) and subsides in the spring (March or April). The onset and severity of the symptoms are highly individualized and depend, in part, on where you live.

The number of cases and severity of symptoms increase with distance from the equator. For example, people near the Arctic Circle tend to experience more severe SAD starting earlier in the fall than people in the Caribbean. A true SAD diagnosis can be made only after symptoms have lasted over the past two winters for at least four weeks each time.

The symptoms of SAD can range from mild to severe. They may simply be a nuisance to live with or severe enough to affect your ability to function. People who experience mild symptoms but aren't diagnosed with SAD are often described as having the "winter blues" or "subsyndromal SAD." Three to five percent of Americans have SAD and about another 10% have subsyndromal SAD.

Women experience SAD three to four times more often than men. This disorder affects people of any racial or ethnic group, and it can occur at any age—though it is mostly seen in people in their twenties through forties. Even children can be affected by SAD; however, they may experience different symptoms than adults. For example, children are more likely to be irritable instead of sad or anxious.

Common Symptoms of Seasonal Affective Disorder

The following symptoms typically begin in the fall, intensify in winter, and subside in spring:

  • Decreased energy and activity
  • Tiredness, sleep more
  • Sadness, anxiety
  • Appetite changes (usually increased appetite)
  • Carbohydrate craving
  • Weight gain
  • Loss of interest in sex
  • Withdrawal from friends and family
  • Difficulty concentrating and accomplishing tasks
  • ]]>Premenstrual syndrome]]> in women (worsens or only occurs in winter)

How Does SAD Differ From Other Types of Depression?

The main difference between SAD and other types of depression is that SAD occurs only during the winter months. In many types of depression, people generally eat and sleep less and lose weight; people with SAD usually eat and sleep more and gain weight when it is cold and dark outside.

SAD, like other types of clinical depression, is not caused by psychological or social factors, although such stresses can aggravate it. Normal sadness tends to be situational and does not generally include these physical symptoms.

The "holiday blues" can be distinguished from SAD because they are generally not accompanied by physical symptoms. They are caused by the typical stresses of the December holiday season and occur only around the holidays.

What Causes SAD?

Lack of exposure to light seems to be the main trigger of SAD symptoms. There are a variety of hypotheses as to the underlying biochemical process that is affected by the lack of light. Also, SAD appears to run in families. Most people with the disorder have at least one close relative who has had bouts of depression (often SAD) at some time.

An abnormality in one or more neurotransmitters and/or hormones is the suspected cause of SAD. Neurotransmitters are the chemicals that carry messages between nerve cells. A deficiency of the neurotransmitter serotonin is considered to be a likely cause of SAD. Its concentration in the brain varies with the seasons, the smallest amount occurring during the winter.

Other chemicals under investigation include the neurotransmitters norepinephrine and dopamine, and the hormone melatonin. The female sex hormones estrogen and progesterone may also be involved, since women are more vulnerable to SAD than men—especially in the years between puberty and ]]>menopause]]> .

How Can SAD Be Treated?

Light Therapy

Light therapy is the primary treatment for SAD. In some studies, light relieves symptoms in 75% of SAD patients within 2-14 days. Scientists believe that light entering through the eye may modify brain chemistry, correcting the abnormalities resulting from a lack of light. While light therapy almost certainly works, only a relatively small number of studies have been rigorous enough to offer scientific proof of light therapy’s effectiveness.

In this treatment, a person is exposed to light that is 5-20 times brighter than regular indoor lighting by sitting close to a light box for 15 minutes to a few hours a day. Since looking directly at the light is not recommended, usual activities such as reading, writing, and eating can be carried out. The length of time and intensity of the light can vary depending on a person's needs and the equipment used. Initial evaluation and ongoing supervision of treatment should be provided by a healthcare professional who has experience with light therapy.

Although light therapy is safe for most people, it can cause eyestrain, ]]>headaches]]> , ]]>insomnia]]> , and feelings of restlessness or irritability. These problems can often be resolved by reducing the length of exposure or sitting farther from the light box. People with certain types of eye disease or those taking medications that increase light sensitivity may not be able to use light therapy, or should use it only under closely monitored care from an ophthalmologist.

Lifestyle Changes

Although light therapy is considered the first-line treatment for most people with SAD, there are lifestyle changes you can try instead of, or in conjunction with, light therapy. Some people experience improvement from increasing their exposure to indoor light from regular lamps and to outdoor light by taking daily ]]>walks]]> during the morning or afternoon. Taking a winter vacation in a sunny place with longer days may also help.

Getting regular aerobic exercise can also help improve mood in people with SAD. Its effect is enhanced when done outdoors or in front of a light box. In addition, ]]>exercise]]> and diet can be used to control the weight gain common in SAD. Since stress can exacerbate SAD, ]]>stress management]]> is important, especially during the winter months. Psychotherapy may be useful in coping with problems that are causing stress.


Antidepressant medications can be used to treat SAD, but are usually prescribed with light therapy instead of replacing it altogether. When light therapy is only partially successful, medication may enhance the light's effect. Use of light therapy in conjunction with medication may make it possible to take smaller doses of medication and to reduce medication side effects. In addition, taking medication can decrease the amount of time that is needed in front of lights.

The most frequently used antidepressant medications for SAD are the selective serotonin reuptake inhibitors (SSRIs), such as Prozac, Zoloft, and Paxil. Bupropion (Wellbutrin) and other antidepressants may also be effective. ]]>Bupropion]]> can be prescribed for the prevention of major depressive episodes in patients with a history of SAD.

Research Results

The Can-SAD study was a double-blind, randomized, controlled study performed during three winter seasons in several treatment centers in Canada. The study was scientifically designed to meet the rigor of statistical standards.

Ninety-six patients were randomly assigned for the length of eight weeks to one of the following treatment groups: an intense light treatment and placebo medication, or a placebo (very low intensity) light and medication (Fluoxetine). There were no statistically significant differences between the two modalities of treatment, which basically “supports the effectiveness and tolerability of both treatments for seasonal affective disorders."

Rohan et al performed the first controlled psychotherapy trial for SAD. They compared standard light therapy (LT), SAD goal-oriented cognitive behavioral therapy (CBT), and their combination with delayed LT control (which is LT after 6 weeks of monitoring the patients clinically). For the three modalities of treatment, the results showed "significant reductions in depressive symptoms." Rohan et al recommended that more research needs to be done in this area.

Other treatments with possible benefit are still being investigated. These include melatonin, L-tryptophan, and vitamin d supplementation.

What Is the First Step in Treating SAD?

If you have mild SAD symptoms, start by increasing your exposure to regular indoor and outdoor light. Try starting a walking program or a daily exercise regime. If you have symptoms that are significantly interfering with your quality of life, you should consult your healthcare provider and/or a mental health professional. He or she can determine whether you do have SAD and discuss available treatments. Remember, there are a number of different treatment options that can be used alone or in combination that can help you feel better and keep a brighter outlook on winter.