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What’s the Difference Between Seasonal Affective Disorder and Depression?

Nicky Lowney
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Difference between SAD and depression
For those of us living in colder climates, shorter days bring sweater weather, holidays, and snow-covered trees. But for many of us, they can also bring episodes of extreme sadness and fatigue. If you experience substantial changes in mood with the arrival of fall and winter, you may wonder if you suffer from severe depression or seasonal affective disorder (SAD).

If you’re wondering what SAD is, and how it’s different from depression, read on for the top 10 things to know about this condition. And if you’re considering talking to a professional about SAD or other mental health issues, check out our list of the best online therapy sites.  

If you or someone you know is suffering from debilitating depression or suicidal thoughts, it is important to seek emergency help right away. Call your national suicide prevention hotline or emergency services.

1. SAD is a subtype of major depression

Mental health experts do not consider SAD to be a separate mental health disorder from depression. Rather, it is a subtype of major depression. Several key symptoms that SAD shares with major depression include:

  • Sadness 
  • Hopelessness 
  • Changes in appetite 
  • Changes in sleep patterns 
  • Changes in energy levels
  • Loss of interest in usual activities
  • Difficulty concentrating
  • Suicidal thoughts (If you are having suicidal thoughts, seek help immediately)

It is important to note that people with major depression or SAD may experience a variety of symptoms; not everyone experiences all of these symptoms.

2. SAD has key differences from depression

The main difference between SAD and depression is the seasonality of the condition. SAD tends to come back every year at the same time. People with SAD experience sustained low moods for more than two weeks—as they may with depression--but it’s usually limited to the winter months. Symptoms may include overeating (usually involved excessive cravings for carbohydrates), weight gain, oversleeping, and retreating from social activities (a feeling of needing to “hibernate”).

Winter-specific SAD tends to take a more lethargic form than the irritability that is often seen in depression. People with winter SAD are more likely to overeat than to undereat, and more likely to oversleep than to have insomnia. Usually symptoms of SAD begin to appear in the fall: when days get shorter, symptoms get worse, and symptoms disappear when the days get longer again. Typically, symptoms of SAD last for four to five months of the year and often--but not always--recur each year. Infrequently, people experience SAD during the summer months. 

3. SAD also has a connection with bipolar disorder

People with bipolar disorder are more susceptible to SAD. Research reveals that 15-22% of patients with bipolar disorder experience seasonality in their symptoms: typically, episodes of mania may be triggered in the spring and summer, characterized by anxiety, agitation, and irritability. Then as days get shorter, depressive episodes--along with characteristic lethargy, oversleeping, and overeating--are more likely to occur.

4. SAD is not “the winter blues”

Winter can be a difficult and long season for many of us who live in cold climates. There are some lifestyle habits that can help you get through the season with a better outlook: read here for tips on how to stave off winter depression. But clinical SAD is more severe than the winter blues. While the winter blues may have you feeling down, you will probably be able to do what you need to do to get through the day. With SAD, depressive episodes may make everyday tasks impossible. If you are missing work, school, or other important activities because of extreme lethargy, sadness, or hopelessness, you should seek professional help. 

5. SAD is not the same as an episode of major depression that occurs in winter

Stressful holidays can trigger depressive episodes in people with depression. If you have an existing diagnosis of depression and have experienced depressive episodes at other times of the year, feeling depressed in the winter is probably not a sign of a new diagnosis of SAD. For many people, traumatic memories associated with winter or holidays can trigger depressive episodes. This differs from SAD, which is triggered by the actual change in season.

6. SAD may be connected to a person’s levels of serotonin and/or melatonin

Although all the causes of SAD are not fully understood, researchers believe that it is triggered by imbalances in certain brain chemicals. Like major depression, SAD could be caused by an imbalance in serotonin, a chemical that helps regulate mood. Sunlight helps the body control the maintenance of serotonin levels. In people with SAD there may be a dysfunction in this system. There is also research that suggests that people with SAD may have an overproduction of melatonin, which is essential for controlling the circadian sleep cycle.

With too much melatonin, high levels of sleepiness are produced, which helps explain the characteristic lethargy experienced by people with SAD. Serotonin and melatonin are key in controlling a normal sleep-wake cycle. In people with SAD, this may be unbalanced, leading to changes in mood and sleep. Because SAD is connected to light levels, regions farther away from the equator—like Alaska-- see higher rates of SAD than those closer to the equator, like Florida. 

The National Institute of Mental Health has a fact sheet about SAD that discusses the causes of SAD.

7. For SAD and any depressive episodes, get medical help

If you feel sad or hopeless for days at a time, it’s important to seek professional help. A professional will be able to diagnose you, whether it’s winter blues, SAD, major depression, or other mental health conditions. A diagnosis of SAD usually involves a therapist and client using specific questionnaires to confirm the diagnosis.

In order to officially diagnose you with SAD, your healthcare provider will see if you have the symptoms of the condition, with depressive episodes occurring during specific seasons for at least two years, and episodes that are more frequent than depressive episodes at other times during the year. They will be able to develop an individualized treatment plan from there. But whether or not your diagnosis is officially recognized as SAD, it is important to work with a professional to treat your symptoms. 

8. Some therapies for SAD are similar to those for major depression

Cognitive behavioral therapy is a form of talk therapy that teaches people to replace harmful or negative thoughts with positive ones. It has been adapted for the treatment of SAD, so that patients are taught to replace negative thoughts about winter with positive ones. It is often conducted over the course of 6 weeks or so.

Because of its connection to serotonin functioning, SAD responds to selective serotonin reuptake inhibitors (SSRIs) like fluoxetine and sertraline. These can only be prescribed by a medical professional. Like all medications, they have side effects. You will have to work with your doctor to see if an antidepressant is right for you. If you are considering telehealth therapy, check out Cerebral, a mental health subscription service that employs board-certified psychiatrists and other professionals to manage anxiety, depression, insomnia, and other mental health conditions.

9. Light therapy is an effective treatment option for SAD

Unlike major depression, SAD is responsive to light therapy. Its purpose is to make up for the lower levels of sunlight in colder climates in winter that is believed to trigger the imbalances that cause symptoms of SAD. Light therapy involves sitting in front of a light box for 30-45 minutes in the morning, from fall through spring. These boxes are stronger than everyday sunlight, but with harmful UV rays filtered out. They are safe for most patients but -can be difficult to tolerate for people with certain eye conditions. 

10. Vitamin D has seen mixed results as a treatment for SAD

Some researchers believe that vitamin D may be lacking in some people with SAD. Vitamin D is connected to serotonin activity, and we receive it through food and through sunlight. Less sunlight in winter months can lead to a deficiency in vitamin D, possibly disrupting serotonin and therefore interfering with mood regulation. Research has found mixed results when testing vitamin D alone as a treatment for SAD.


While all of us may experience some blues when the days get shorter, episodes of depression, lethargy, and severe sadness can be a sign of SAD. With any depressive episodes, it is important to speak with a trained therapist. Our list of best online therapy sites is a good place to start if you are considering working with a mental health professional in a virtual setting.

Nicky Lowney
Nicky Lowney is an accredited health communication expert and writer for Top10. Having worked extensively in the pharmaceutical industry, Nicky specializes in translating complex medical information into content that informs and helps people. Nicky has also written for Tufts University School of Dental Medicine, and Decision Resources Group, among others.

The author of this article has been paid by Natural Intelligence to write this article. Neither the author nor Natural Intelligence provide medical advice, diagnosis, or treatment. If you think you may have a medical emergency, call your doctor or your local emergency number immediately.