Seasonal Affective Disorder: What It Is and How to Treat It

Seasonal Affective Disorder: What It Is and How to Treat It

Seasonal affective disorder (SAD) is a kind of depression related to the seasons of the year. Most commonly, SAD, also called winter depression, starts in the late fall or early winter and lasts through the winter months. This is called winter-pattern SAD. 

Some people experience SAD in the spring and summer months (summer-pattern SAD), but this is less common. Typically, symptoms last 4-5 months a year and repeat each year.

Risk Factors for SAD

Experts at the National Institute of Health (NIH) say that millions of Americans may suffer from seasonal depression, although only a fraction of them have been diagnosed. Women are more likely than men to experience seasonal affective disorder, as are those who live far from the equator where seasonal weather changes and daylight hours are more extreme. 

People with major depressive disorder, bipolar disorder and other mental disorders such as anxiety disorder, schizophrenia and attention-deficit/hyperactivity disorder (ADHD) are at a higher risk for seasonal affective disorder. A propensity toward SAD runs in families, so if other members of your family experience seasonal affective disorder, you are at higher risk.

Symptoms of SAD

SAD has general symptoms, which are the same as those of major depression. These include: 

  • Feeling depressed most of the time
  • Losing interest in activities that you once enjoyed
  • Persistent low energy
  • Feeling hopeless or worthless
  • Difficulty concentrating
  • Frequent thoughts of death or suicide

In addition, SAD sufferers may have the following symptoms depending on whether it is winter-pattern or summer-pattern SAD:

  • Winter-pattern
    • Sleeping too much
    • Overeating, especially with carbohydrate cravings
    • Weight gain
    • Withdrawing from others
  • Summer-pattern
    • Trouble sleeping (insomnia)
    • Poor appetite
    • Weight loss
    • Restlessness and agitation
    • Anxiety
    • Violent outbursts

Causes of SAD

Although science does not completely understand what causes seasonal affective disorder, they do have some clues. 

Too Little Serotonin 

Serotonin is a chemical in the brain that regulates mood. In most people, the level of sunlight helps maintain healthy serotonin levels, but this mechanism does not work properly in people with SAD. Scientist believe that vitamin D produces serotonin. 

You can get vitamin D from sunlight, as a supplement and in foods such as red meat, egg yolks and fatty fish like salmon. If the body does not efficiently use vitamin D to produce serotonin, then in the winter months when the days are shorter and there is less daylight, serotonin levels can drop too low. Vitamin D deficiency is common; about 40% of Americans do not get enough of it.

Too Much Melatonin

Melatonin is a hormone that is key to maintaining a normal sleep-wake cycle. The bodies of those who experience SAD produce an abundance of melatonin, making them overly sleepy.

Along with the level of light, melatonin and serotonin regulate the body’s circadian rhythm, the natural cycle of sleep and wakefulness. An imbalance of either melatonin or serotonin along with reduced light levels can trigger seasonal depression in those who are prone to it.

Treatments for SAD

Talk to your healthcare provider about getting treatment for SAD. There are several treatments available and they can be combined when indicated.

Light Box Therapy

Since the major factor contributing to SAD is the lower light levels during fall and winter, the main treatment for SAD is light box therapy. With this approach, SAD sufferers would purchase a special seasonal depression lamp. SAD light therapy consists of sitting about 16 to 24 inches in front of the SAD lamp every morning for 30-45 minutes from the fall until the spring. The SAD lamp is about 20 times brighter than regular indoor lighting and filters out harmful UV light. Sitting in front of the seasonal affective disorder lamp daily counteracts the reduced sunlight in the winter months.

SAD light therapy is not for everyone. If you are particularly sensitive to sunlight or have certain eye diseases, you may need to either use light box therapy under medical supervision or explore other alternatives.

An effective SAD light has the following features: 

  • It is made specifically to treat SAD – Some lightbox therapy lamps are designed to treat skin disorders, not SAD. In addition to not helping alleviate SAD symptoms, these therapy lamps emit UV light, which can damage your eyes.
  • It is very bright – In order to make a difference in your mood, the seasonal depression lamp needs to be significantly brighter than your regular indoor lighting. The recommended light intensity is 10,000 lux.
  • It does a good job of filtering out UV light – Since you need to keep your eyes open when doing your light box therapy (but not looking directly at the lamp), it is important that the SAD light filters out all or most of the UV light. 

You can buy a lightbox therapy lamp without a prescription. SAD lights generally cost between $30 and $130; most insurance plans do not cover their cost.


A type of “talk therapy” that has been successful in treating seasonal depression is cognitive behavioral therapy (CBT-SAD). Look for a group therapy setting specifically for SAD. Therapy is typically twice a week for 6 weeks. The therapy helps participants to identify happy, positive thoughts and associate them with the winter season and encourages them to engage in pleasant, fun activities during winter to create positive associations. According to the NIH, light therapy works faster than CBT, but the benefits of CBT were longer lasting.

Medications and Supplements

Since a vitamin D deficiency can exacerbate SAD symptoms, some doctors recommend vitamin D nutritional supplements. In more extreme cases, doctors may prescribe antidepressant medication such as fluoxetine, citalopram, sertraline, paroxetine and escitalopram. These medications are called selective serotonin reuptake inhibitors (SSRIs) because they balance the serotonin levels in the brain and improve mood. Another antidepressant used to treat SAD is extended-release bupropion. Since antidepressant drugs have different side effects, you may need to try several out before you find one that works for you.