Overview, Causes, & Risk Factors

Seasonal affective disorder, or SAD, is a condition that causes lengthy bouts of severe depression during certain seasons of the year, especially winter.

What is going on in the body?

When a person has seasonal affective disorder, he or she experiences depression during a specific season. This condition may happen during any season, but it appears to be more common during the winter. Often SAD begins in the fall and continues through the winter until early summer.

What are the causes and risks of the condition?

Although the cause of SAD is not completely clear, one of the suspected causes is an increased level of melatonin in the blood system. Melatonin is a hormone secreted by a gland in the brain. Melatonin increases the need and desire to sleep. When it is dark, the body produces more melatonin. The more darkness in the day, the more melatonin is produced.

Less sunlight may also have an effect on a person's "biological clock." A person's body may not adjust to the change in routine due to time changes and daylight changes. Other causes of SAD may include changes in the body's temperature cycle and hormonal changes.

SAD is four times more common in women than in men. SAD sometimes occurs in children but appears to be more common after the age of 20 years. SAD also appears to be more common in people living in the northern states as compared to those in the southern states.

Symptoms & Signs

What are the signs and symptoms of the condition?

Symptoms associated with SAD can vary, depending on how severe the condition is. Symptoms include:

These symptoms usually occur during the "seasonal period" that affects a person and then goes away after that particular season. The symptoms then tend to reappear the following year at the same time.

Diagnosis & Tests

How is the condition diagnosed?

Diagnosis begins with a history and physical exam. This may be all that is needed to make the diagnosis of SAD. In other cases, further testing is needed to rule out physical or other medical problems that may be causing SAD. A person may also need to consult with and be evaluated by a healthcare professional trained in treating depression.

Prevention & Expectations

What can be done to prevent the condition?

Since the cause of SAD is not yet clear, preventing SAD may not be possible. A person should see a healthcare provider for treatment of depression or feelings of severe sadness. This may decrease the risk of developing SAD.

What are the long-term effects of the condition?

There are no expected long-term complications if SAD is treated and monitored carefully.

What are the risks to others?

SAD is not contagious and poses no risk to others.

Treatment & Monitoring

What are the treatments for the condition?

The treatment for SAD depends on whether any other conditions exist. It may help to increase the amount of light in the house and workplace. Taking walks during the day to absorb more light may also decrease symptoms of SAD. A person with SAD may have light therapy sessions in which they sit by a special "light-box" or wear a special light cap. These devices have special fluorescent lights. The person uses these devices for a certain number of minutes each day. Medications, such as antidepressants, may also be needed. In many cases of SAD, a person may be referred to a therapist for behavioral therapy.

What are the side effects of the treatments?

Side effects to treatment will depend on the treatment used. Side effects to light therapy include sensitivity to the light, especially in the eyes. Light therapy can also cause:

Antidepressant medications may cause:

What happens after treatment for the condition?

In some cases, SAD may be temporary and no treatment may be necessary. In a majority of cases, though, treatment may need to continue for a lifetime. A person may be able to carry out treatment at home and follow up with the healthcare provider or therapist.

How is the condition monitored?

SAD is monitored by a person's own feelings and symptoms. If symptoms continue or progress, such as a feeling of hopelessness or severe depression, the person should contact the healthcare provider.