What are the symptoms of seasonal affective disorder (SAD)?

Many of us feel a little bit sad when winter approaches. The days feel shorter, the weather gets darker and colder, schedules get busier, and the holidays add stress. 

But if this sadness is severe enough to affect your ability to function on a day-to-day basis, it might be more than just the winter blues. You might be experiencing a condition known as Seasonal Affective Disorder, or SAD. 

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SAD is a condition that causes mood disturbances—either depression, mania, or both. Roughly 5% of people in the United States experience it each year, and it’s most common between ages 20–30 (Kurlansik, 2012; Magnusson, 2005). 

While SAD symptoms are similar to a handful of mental health conditions, it’s really classified as a sub-type of depression or bipolar disorder. But SAD is different from other mood conditions because seasonal changes trigger symptoms (Uher, 2013; Meesters, 2016). 

If we look at the silver lining, symptoms of SAD aren’t constant throughout the year. They begin during specific seasonal transitions, usually starting in late fall or early winter and improving when spring starts. 

You might have heard it called winter depression because it’s so much more prevalent as the days get shorter and darker. Common symptoms of SAD include (APA, 2020): 

• Depressed or sad feelings

• Trouble concentrating

• Excessive tiredness 

• Sleep changes, particularly sleeping too much 

• Loss of interest and ability to enjoy things you usually like

• Increased appetite, especially for carbs like pasta and bread 

• Abnormal movements like fidgeting, pacing, or slow speech and movement

• Suicidal thoughts

Depression vs. SAD: what’s the difference?

Some symptoms of SAD––like unhappiness, trouble focusing, and excessive fatigue––are very similar to the symptoms of major depression. However, there are some differences. 

For example, SAD symptoms often decrease on days that are bright and sunny. Symptoms of Major Depression are unlikely to fluctuate based on the weather. With depression, sleep changes are common. More than 85% of people with depression experience insomnia and trouble falling asleep. In SAD, the opposite is true—most people sleep excessively and have difficulty staying awake (Geoffroy, 2018). 

Diet and appetite are also affected differently. If you’re depressed, your appetite usually decreases, which might lead to weight loss. But with SAD you often feel hungrier. Many people with SAD report uncontrollable cravings––especially for carbohydrates and starchy foods. This can lead to overeating and increased weight gain (Westrin, 2007). 

If you’re experiencing symptoms of SAD, see a mental health professional who can help diagnose and find the best way to treat it. 

They’ll do a careful interview with you to assess your symptoms. Then screening tools like the Seasonal Assessment Form or Seasonal Pattern Assessment Questionnaire are used to track your unique mood pattern based on the seasons.  

There are several theories about what causes SAD. Many researchers suggest it’s related to the circadian rhythm, which is essentially your internal clock. These biological rhythms affect your mood, behavior, and other elements, and the changes occur on a 24-hour cycle. 

Circadian rhythms are affected by the light-dark cycle. In winter there are fewer hours of sunshine, especially as you get further North, which increases melatonin production (a hormone produced when it’s dark) and reduces serotonin (a hormone that helps keep your mood stable). These hormonal changes can lead to depression (Sohn, 2005, Willeit, 2011). 

Since darker days trigger SAD, can light exposure treat it? It turns out, it can. 

Bright light therapy using a light box or SAD lamp is one of the primary treatments. Exposure to light at specific intervals, or gradually increasing light during the last hours of sleep (a technique called dawn simulation) can reverse some symptoms of SAD (Pail, 2011; Terman, 2006). Some studies suggest that dawn simulation has been more effective than other forms of SAD treatment (Avery, 2001). 

Since serotonin levels are low in people with SAD, antidepressants that regulate serotonin (selective serotonin reuptake inhibitors or SSRIs) are another helpful option. In studies, the SSRI fluoxetine (see Important Safety Information) was as effective at treating SAD as light therapy. Another SSRI bupropion (see Important Safety Information) is FDA-approved to treat SAD (NAMI, 2016; Lam, 2006). 

Psychotherapy and cognitive behavioral therapy are also helpful in treating SAD. Beyond therapy, there are also things you can do on your own to boost these effects. Regular sleeping patterns, good sleep hygiene, exercise, and time outdoors are all healthy ways that can reduce symptoms of SAD. 

It’s essential to be aware that your winter blues may be something more serious––like SAD. Even though we don’t know precisely where SAD comes from, there are ways to treat it and improve your quality of life. 

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Current version

November 24, 2021

Written by

Gina Allegretti, MD

Fact checked by

Yael Cooperman, MD

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About the medical reviewer

Yael Cooperman, MD, Ro

Yael Cooperman is a physician and works as a Senior Manager, Medical Content & Education at Ro.