Seasonal affective disorder, or SAD, is a type of depression that occurs during the same season each year. You may have SAD if you felt depressed during the last two winters but felt much better in spring and summer.
Anyone can get SAD, but it’s more common in:
- People who live far from the equator, where winter daylight hours are very short.
- People between the ages of 15 and 55. The risk of getting SAD for the first time goes down as you age.
- People who have a close relative with SAD.
SAD is sometimes called winter depression or seasonal depression.
What causes SAD?
Experts aren’t sure what causes SAD. But they think it may be caused by a lack of sunlight. Lack of light may:
- Upset your “biological clock,” which controls your sleep-wake pattern and other circadian rhythms.
- Cause problems with serotonin, a brain chemical that affects mood.
What are the symptoms?
If you have SAD, you may:
- Feel sad, grumpy, moody, or anxious.
- Lose interest in your usual activities.
- Eat more and crave carbohydrates, such as bread and pasta.
- Gain weight.
- Sleep more but still feel tired.
- Have trouble concentrating.
Symptoms come and go at about the same time each year. Most people with SAD start to have symptoms in September or October and feel better by April or May.
How is SAD diagnosed?
It can sometimes be hard to tell the difference between SAD and other types of depression because many of the symptoms are the same. To diagnose SAD, your doctor will ask if:
- You have been depressed during the same season and have gotten better when the seasons changed for at least 2 years in a row.
- You have symptoms that often occur with SAD, such as being very hungry (especially craving carbohydrates), gaining weight, and sleeping more than usual.
- A close relative—a parent, brother, or sister—has had SAD.
Your doctor may also do a mental health assessment to get a better idea of how you feel and how well you are able to think, reason, and remember.