Shining a Light on Seasonal Affective Disorder

Seasonal affective disorder (SAD) is a type of depression linked to decreased exposure to daylight. Learn how light can help beat these winter blues.

Pearl is 28, and since she was a teenager, her moods have followed the seasons like clockwork. She sinks into depression when the days shorten in October and still feels gloomy during her birthday in January. She slowly comes out of her funk in March.

According to her doctor, Pearl has seasonal affective disorder (SAD), a type of depression linked to decreased exposure to daylight. SAD can occur in the summer, but it typically occurs in the darker months of late autumn and winter.

SAD can strike anyone, but it most often affects women. Symptoms usually start between the ages of 18 and 30. The chance of developing SAD decreases with age.

What causes SAD?
Your heartbeat, blood pressure, hormones, breathing and other bodily functions rise and fall in a 24-hour pattern called circadian rhythm. For some people, decreased exposure to sunlight throws off their circadian rhythm and can lead to symptoms associated with SAD.

It's not clear why some people get seasonal depression and others don't. But scientists believe that reduced daylight may boost the body's production of melatonin. Melatonin is a sleep-related hormone that may cause symptoms of depression.

What are the symptoms?
Common symptoms of SAD include:

  • Symptoms of depression, such as fatigue, low self-esteem, loss of interest in normal activities and withdrawal from family and friends
  • Weight gain and cravings for carbohydrates, especially sweets and starchy foods
  • Oversleeping or trouble waking up in the morning

A doctor may diagnose SAD if these mood changes have occurred during late autumn and winter for at least three years, with normal or high mood during the spring and summer.

Because the symptoms are similar, SAD is sometimes mistaken for low thyroid (hypothyroidism), low blood sugar (hypoglycemia), a viral infection, severe depression or bipolar disorder. 

How is SAD treated?
First, talk with your doctor or mental health specialist about your symptoms. If he or she finds that you may have SAD, proper treatment can be suggested.

If you have mild symptoms that don't disrupt your life, getting more exposure to light may improve your mood. Try to spend an hour or so outside on sunny days, or arrange your office or home so that you are seated near a window during the daytime.

If your symptoms are more severe, you may need bright light treatment (phototherapy). For this, you sit in front of a special light box each morning for half an hour or longer. The light box emits bright white light that is about 10 times stronger than regular lights.

Phototherapy is highly effective for most people with SAD. If it doesn't completely ease your symptoms, your doctor may suggest the addition of counseling or antidepressant medication.



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