Seasonal Affective Disorder… or just the winter blues?

Do the shorter days in the winter give you the blues? If so, you are not alone. As the winter months draw near and day lights savings begins, the sky gets darker earlier in the day. During this time, people may begin to experience depressive symptoms, otherwise known as Seasonal Affective Disorder, where there are biological and mood disturbances occurring in autumn and winter with remission in the spring or summer (Kurlansik & Ibay, 2012). Seasonal affective disorder (SAD) is a type of depression that is triggered by the changing of seasons, typically coinciding with the beginning of fall. With SAD, the seasonal depression gets worse in the late fall or early winter and ends when it becomes sunnier in the spring. According to the American Psychiatric Association, SAD is officially classified as major depressive disorder with seasonal patterns (Golden, et al., 2005).

How common is Seasonal Affective Disorder?

In the United States about 10 to 20% of people get a milder form of the “winter blues” when you are stuck inside with it getting darker earlier (Seasonal Depression, 2022). Unlike this more common experience, SAD is a form depression that affects people’s daily life including how they feel and think.

Each year, about 5 percent of the US population experiences seasonal affective disorder. The symptoms are present for around 40 percent of the year (Kurlansik & Ibay, 2012). SAD usually starts in young adulthood (typically between the ages of 18 and 30) and tends to affect women more than men. People are also at higher risk for having SAD if they have another mood disorder, such as major depressive disorder, have relatives with SAD or other forms of mental health conditions, live at latitudes either far north or south from the equator where there is less sunlight during the winter, and live in cloudy regions (Seasonal Depression, 2022).

What are the symptoms of Seasonal Affective Disorder?

Symptoms comprise of mood changes and signs of depression (Seasonal Depression, 2022), including:

  • Sadness, feeling depressed most of the day, almost every day.
  • Anxiety.
  • Carbohydrate cravings and weight gain.
  • Extreme fatigue and lack of energy.
  • Feelings of hopelessness or worthlessness.
  • Trouble concentrating.
  • Feeling irritated or agitated.
  • Limbs (arms and legs) that feel heavy.
  • Loss of interest in usually pleasurable activities, including withdrawing from social activities.
  • Sleeping problems (usually oversleeping).
  • Thoughts of death or suicide. 

What causes Seasonal Affective Disorder ?

Although SAD is a major depressive disorder, researcher do not know exactly what causes it, but believe that lack of sunlight may trigger the condition if someone is prone to getting it (Seasonal Depression, 2022). 

Theories of causes include but are not limited to:

  • Biological clock change: When there’s less sunlight, your biological clock shifts. Your mood, sleep, and hormones are regulated by your internal clock and when it shifts, you are not fully adjusted to the changes in daylight length and the effects is has on your daily schedule. 
  • Brain chemical imbalance:  If you’re at risk of SAD, you may already have less serotonin activity. Since sunlight helps regulate serotonin, a lack of sunlight in the winter can make the situation worse. Serotonin levels can fall further, leading to depression.
  • Vitamin D deficiency: Your serotonin level also gets a boost from vitamin D. Since sunlight helps produce vitamin D, less sun in the winter can lead to a deficiency in vitamin D that can affect your serotonin level and your mood.
  • Melatonin boost: Melatonin is a chemical that affects your sleep patterns and mood. The lack of sunlight may stimulate an overproduction of melatonin in some people. You may feel sluggish and sleepy during the winter.
  • Negative thoughts: People with SAD often have stress, anxiety and negative thoughts about the winter. Researchers aren’t sure if these negative thoughts are a cause or effect of seasonal depression.

How is Seasonal Affective Disorder diagnosed?

When having symptoms of seasonal affective disorder (SAD), it is best to see your healthcare provider for an evaluation rather than try to self-diagnose. Typically, SAD is part of a more complex mental health issue, so it is beneficial to investigate other possible causes of the depression (Seasonal Depression, 2022).  

How is Seasonal Affective Disorder (SAD) treated?

When you go to your healthcare provider, they will discuss a variety of treatment options including (Seasonal Depression, 2022):

  • Light therapy: Bright light therapy, using a special lamp, can help treat SAD.
  • Cognitive behavioral therapy (CBT): CBT is a form of talk therapy. Research has shown it effectively treats SAD, producing the longest-lasting effects of any treatment approach.
  • Antidepressant medication: Sometimes, providers recommend medication for depression, either alone or with light therapy.
  • Spending time outdoors: Getting more sunlight can help improve your symptoms. Try to get out during the day. Also, increase the amount of sunlight that enters your home or office.
  • Vitamin D: A vitamin D supplement may help improve your symptoms.

Light Therapy

Typically, many individuals experiencing Seasonal Affective Disorder use light therapy as their main source of treatment and may combine it with others as well. Using bright white light for SAD was first described in 1984 (Rosenthal et al., 1984). Light boxes are designed to deliver a therapeutic dose of bright light to treat symptoms of SAD (Mayo Foundation for Medical Education and Research, 2022). There are many types of light boxes on the market, but successful light therapy treatment requires a specific type of lamp that has white fluorescent light tubes covered with a plastic screen to block harmful ultraviolet rays. The light intensity should be 10,000 lux, and about 20 times brighter than regular indoor light.  To use this treatment, individuals should be positioned about 12 to 18 inches from the light source with their eyes open, although they do not need to stare directly into the light. You can use the light box while reading, eating, working, or doing other activities (Kurlansik & Ibay, 2012). The time of day you use light therapy may also impact how effective the treatment is. Light therapy should last for approximately 30 minutes daily in the first hour you wake up in the morning for best results as using light therapy during the day may cause insomnia. The results, when using light therapy, are usually seen within two to four days, but could take about two weeks to reach its full benefits. After seeing results, you should continue to use light therapy throughout the entire winter as SAD symptoms can return when stopping treatment.

Light therapy is typically safe and well-tolerated. But you may need to avoid light therapy if you (Seasonal Depression, 2022):

  • Have diabetes or retinopathies: If you have diabetes or a retina condition, there’s a potential risk of damaging the retina, the back of your eye.
  • Take some medications: Certain antibiotics and anti-inflammatories can make you more sensitive to sunlight. Light therapy can then cause harm.
  • Have bipolar disorder: Bright light therapy and antidepressants can trigger hypomania or mania, uncontrolled boosts in mood and energy level. If you have bipolar disorder, let your provider know. This will play a role in your treatment plan.

When using light therapy, you may experience side effects including eyestrain, fatigue, headaches, insomnia, and irritability.

You should always check with a health care provider if you feel like you might be affected by SAD, but if you are curious about lights, you can look at the following consumer guides:


Danilenko, K. V., & Ivanova, I. A. (2015, April 7). Dawn simulation vs. bright light in seasonal affective disorder: Treatment effects and subjective preference. Journal of Affective Disorders. Retrieved November 10, 2022, from 

Dillon, K., Perling, A., & Redd, N. (2022, October 13). The Best Light Therapy Lamp. The New York Times. Retrieved November 17, 2022, from 

Golden, R. N., Gaynes, B. N., Ekstrom, R. D., Hamer, R. M., Jacobsen, F. M., Suppes, T., Wisner, K. L., & Nemeroff, C. B. (2005). The efficacy of light therapy in the treatment of mood disorders: a review and meta-analysis of the evidence. The American journal of psychiatry162(4), 656–662.

Kurlansik, S. L., & Ibay, A. D. (2012, December 1). Seasonal affective disorder. American Family Physician. Retrieved November 10, 2022, from 

Lanquist, L., Moe, L., & Zhou, T. (2022, May 20). The 8 best light therapy lamps of 2022, tested and reviewed. Verywell Mind. Retrieved November 17, 2022, from 

Mayo Foundation for Medical Education and Research. (2022, March 30). Seasonal affective disorder treatment: Choosing a light box. Mayo Clinic. Retrieved November 10, 2022, from 

Rosenthal, N. E., Sack, D. A., Gillin, J. C., Lewy, A. J., Goodwin, F. K., Davenport, Y., Mueller, P. S., Newsome, D. A., & Wehr, T. A. (1984). Seasonal affective disorder. A description of the syndrome and preliminary findings with light therapy. Archives of general psychiatry41(1), 72–80.

Seasonal Depression (seasonal affective disorder). Cleveland Clinic. (2022). Retrieved November 10, 2022, from 

Shelton, M. (2008, January 19). Snowman Neighbor. Flickr. Retrieved November 17, 2022, from 

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