Our Health Library information does not replace the advice of a doctor. Please be advised that this information is made available to assist our patients to learn more about their health. Our providers may not see and/or treat all topics found herein.
Seasonal Affective Disorder (SAD)
What is seasonal affective disorder (SAD)?
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. Some people may have SAD during the summer months.
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.
You may need to have blood tests to rule out other conditions that can cause similar symptoms, such as low thyroid (hypothyroidism).
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.
How is it treated?
Light therapy is the main treatment for SAD. Medicines and counseling may also help.
Experts think light therapy works by resetting your biological clock. It helps most people who have SAD, and it's easy to use.
There are two types of light therapy:
- Bright light treatment. For this treatment, you place the light box at a certain distance from you on a desk or table. Then you sit in front of it while you read, eat breakfast, or work at a computer.
- Dawn simulation. For this treatment, a dim light goes on in the morning while you sleep, and it gets brighter over time, like a sunrise.
Talk to your doctor about light therapy, and follow the steps that he or she recommends.
Light boxes use fluorescent lights that are brighter than indoor lights but not as bright as sunlight. Ultraviolet lights, full-spectrum lights, tanning lamps, and heat lamps should not be used.
Light therapy is usually prescribed for 30 minutes to 2 hours a day. The amount of time depends on how strong the light is and on whether you are starting out or are have been using it for a while.
You may start to feel better within a week or so after you start light therapy. But you need to stay with it and use it every day until the season changes. If you don't, your depression could come back.
Antidepressant medicines may help people who have SAD. They may be used alone or with light therapy. The most common ones prescribed for SAD include:
- Selective serotonin reuptake inhibitors (SSRIs), such as paroxetine (Paxil) and sertraline (Zoloft). SSRIs are usually tried first.
- Other antidepressants, such as bupropion (Wellbutrin) and venlafaxine (Effexor).
If your doctor prescribes an antidepressant, be sure you take it the way you're told to. Do not stop taking it suddenly. This could cause side effects or make your depression worse. When you are ready to stop, your doctor can help you slowly reduce the dose to prevent problems.
Counseling may also help. Some types of counseling, such as cognitive-behavioral therapy and interpersonal therapy, can help you learn more about SAD, how to manage your symptoms, and how to help prevent future episodes..
What can you do on your own to feel better?
Regular exercise is one of the best things you can do for yourself. Getting more sunlight may help too, so try to get outside to exercise when the sun is shining. Being active during the daytime, especially early in the day, may help you have more energy and feel less depressed.
- Moderate exercise such as walking, riding a stationary bike, or swimming is a great way to get started. But any activities that raise your heart rate—including daily chores—can help, especially if you can do them outdoors or near a sunny window.
- Try to do muscle-building exercises at least 2 times each week, such as weight training or stair climbing.
Moderate exercise is safe for most people. But it's always a good idea to talk to your doctor before you start an exercise program.
Some people try complementary treatments to help with SAD. One example is melatonin, a hormone that may help regulate your biological clock. If you want to use melatonin or other complementary treatments, be sure to check with your doctor first. These medicines may interact with other treatments.
Other Works Consulted
- American Psychiatric Association (2010). Practice Guideline for the Treatment of Patients With Major Depressive Disorder, 3rd ed. Available online: http://psychiatryonline.org/guidelines.aspx.
- Byrne B, Brainard GC (2008). Seasonal affective disorder and light therapy. Sleep Medicine Clinics, 3: 307–315.
- Melatonin (2009). Review of Natural Products. St. Louis: Wolters Kluwer Health.
- Provencio I (2009). Chronobiology. In BJ Sadock et al., eds., Kaplan and Sadock's Comprehensive Textbook of Psychiatry, 9th ed., vol. 1, pp. 198–210. Philadelphia: Lippincott Williams and Wilkins.
- Sadock BJ, Sadock VA (2007). Mood disorders. In Kaplan and Sadock's Synopsis of Psychiatry, 10th ed., pp. 527–562. Philadelphia: Lippincott Williams and Wilkins.
- Shirani A, St Louis EK (2009). Illuminating rationale and uses for light therapy. Journal of Clinical Sleep Medicine, 5(2): 155–163.
- U.S. Department of Health and Human Services (2008). 2008 Physical Activity Guidelines for Americans (ODPHP Publication No. U0036). Washington, DC: U.S. Government Printing Office. Available online: http://www.health.gov/paguidelines/guidelines/default.aspx.
- Westrin A, Lam RW (2007). Seasonal affective disorder: A clinical update. Annals of Clinical Psychiatry, 19(4): 239–246.
Current as of: September 23, 2020
Author: Healthwise Staff
Kathleen Romito MD - Family Medicine
Alfred Lewy MD, PhD - Psychiatry
To learn more about Healthwise, visit Healthwise.org.
© 1995-2021 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.