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What is seasonal affective disorder or “winter depression?” 

Written by Jennifer Fuller

Published: Dec 27, 2023

Medically Reviewed by Dr. Geralyn Dexter

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If you’re like many people in the U.S., you may feel a bit down during wintertime and even during other seasons. Sometimes, the trigger for winter and other depression that can benefit from treatment is the stress of the holidays. This is what we often call the “winter blues” or “winter depression.” But, for some people, the blues are something more serious – seasonal affective disorder or SAD. But just what is seasonal affective disorder?

Seasonal affective disorder differs from the winter blues. People with SAD don’t just feel “down” during certain seasons — they go through a full depressive episode. However, with treatment, you can manage symptoms of depression, including seasonal depression.

In this article, we discuss what is seasonal affective disorder, its symptoms, causes, and how you can cope with it as winter — or your trigger season — approaches.

What is seasonal affective disorder? 

Seasonal affective disorder, also called SAD or seasonal depression, is a mental health condition that causes people to go through depressive episodes during certain seasons. Unlike other people with major depression, who can be affected by symptoms at any time, people with seasonal affective disorder start experiencing depression symptoms at the same time every year. 

Most people with seasonal affective disorder become depressed during the cold winter months (fall and winter) – however, according to MedlinePlus, about 10% of people affected experience seasonal depression in the spring or summer.

According to psychiatry.org, around 5% of American adults are affected by SAD — that’s more than 10 million people. People who live in more northern latitudes are more likely to be impacted.

Although many of us feel down during the dark winter days, seasonal affective disorder is much more serious than the “winter blues.” Just like any other mental health condition, seasonal depression requires treatment — it’s unlikely to go away on its own.

What month does seasonal depression start?

For most people, symptoms of seasonal affective disorder start around October, when the days get shorter and temperatures drop. Symptoms typically last for around 5 months. If your state participates in daylight savings, you may notice symptoms start after daylight savings time ends.

Some people experience seasonal affective disorder in the summer months, too. For these people, symptoms may appear at the start of summer or when daylight savings begins.

What’s the difference between seasonal and chronic depression?

Chronic depression, officially diagnosed as persistent depressive disorder, is a mood disorder that causes people to experience symptoms of depression almost all the time for 2 years or longer. The symptoms may not be as severe or debilitating as symptoms of a major depressive episode, like suicidal thoughts or hopelessness (although they can be), but they never really go away.

On the other hand, the symptoms of seasonal affective disorder go away at some point during the year. People with SAD start to feel depressed as the seasons change — usually during the transition into winter — but their symptoms disappear during other seasons. 

If you feel depressed all year long but experience worse symptoms during certain seasons, you may be living with persistent depressive disorder (chronic depression) — not SAD. The only way to know is to get an evaluation from a licensed mental health professional.

What causes seasonal depression?

Like with most chronic health conditions, no one knows what causes some people to develop seasonal affective disorder. It probably doesn’t have one singular cause. However, research from the National Institute of Mental Health (NMH) has found that several biological factors may play a role in seasonal depression.

Reduced sunlight and circadian rhythms

The level of sunlight available in the winter is an important factor in the development of seasonal depression. This is why winter-pattern seasonal depression is much more common in people living farther away from the equator — where the days get shorter during winter months.

The reduced level of sunlight (or, for summer-pattern SAD, the excessive amount of sunlight) can affect your body’s biological clock — also known as the circadian rhythm. Every living creature has a circadian rhythm, which impacts the sleep-wake cycle and body temperature regulation, among other important processes. 

Experts believe that the disruptions to your circadian rhythm caused by the changing sunlight levels can cause symptoms of depression.


You may have also heard of — or even taken the supplement — melatonin, a hormone that helps you sleep and plays a role in mood. Seasonal changes (and lack of sunlight) can cause your body to release too much melatonin, which can lead to depression symptoms like fatigue, hypersomnia (sleeping too much), and low mood.

On the other hand, for those with spring- or summer-pattern seasonal depression, increased sunlight can cause your body to produce insufficient levels of melatonin. This can also lead to depression and anxiety.


Serotonin is another hormone that plays a role in both chronic and seasonal depression. Serotonin is a neurotransmitter that’s important for regulating mood. People with depression have less stable levels of serotonin in their brains. The lack of sunlight may make this even worse for people with seasonal depression.

There are other risk factors for developing SAD. These include:

  • Gender: A study on gender differences found that women are more likely to have seasonal depression than men, although some experts dispute this.
  • Other mental health conditions: People who have a history of depression or bipolar disorder are more likely to develop seasonal affective disorder (SAD).
  • Family history: People with seasonal affective disorder are more likely to have a family member who also has it.
  • Location: People who live farther from the equator are more likely to develop SAD because they experience greater fluctuations in seasonal sunlight.

What are the symptoms of seasonal affective disorder?

Generally, seasonal affective disorder shares symptoms with major depressive disorder (often called clinical depression). The main difference is that if you live with SAD, you only experience symptoms during certain months of the year.

Symptoms of SAD include:

Depressed mood: Persistent low mood, sad feelings, or lack of interest

Low energy: Fatigue and lethargy or a noticeable decrease in energy levels

Sleep changes: Significant changes in sleep patterns, like sleeping more or less than usual

Weight changes: Significant changes in appetite and weight

Difficulty concentrating: Trouble focusing or making important decisions; becoming easily distracted

Irritability: Being more moody, irritable, or “snappy” than usual

Loss of interest: No longer feeling interested in activities or hobbies that were once enjoyable or engaging

Feelings of hopelessness or worthlessness: Ongoing negative thoughts about yourself, the future, or life in general

Suicidal thoughts: Thoughts of hurting yourself or ending your life

Physical symptoms: Aches and pains or other physical symptoms that can’t be attributed to a specific medical condition

There are some symptoms unique to winter depression that are important to watch for. These symptoms may not apply to summer-pattern seasonal depression but are often core features of winter-pattern seasonal depression.

5 symptoms specific to seasonal affective disorder (winter pattern)

  • Hypersomnia, or sleeping too much. Typically, people with depression tend to experience insomnia or an inability to fall asleep. For people with winter depression, it’s the opposite — they sleep too much. You might find yourself reluctant to get out of bed or feel lethargic no matter how many hours you’ve slept.
  • Craving carbohydrates. This is a unique symptom of winter seasonal depression that isn’t often seen in people with chronic or major depression. If you live with SAD, you may find yourself hungrier than usual and craving different foods for comfort — especially carbs. If you’re craving more bread, baked goods, and pasta than usual, it can indicate you have SAD.
  • Weight gain. Many people gain weight because of the increased appetite that tends to come along with winter-pattern SAD. People with other types of depression may also experience weight changes, but weight gain tends to be a more pronounced feature of seasonal depression.
  • Feeling desperate for sunlight. One important factor that contributes to seasonal depression in the winter is the increased hours of darkness. The sun goes down very early, especially if you live in the North — which can affect important physiological processes described earlier. Many people who have winter depression report experiencing intense cravings for sunlight.
  • Social withdrawal. Social withdrawal is a shared symptom across all types of depression. But for people with seasonal depression, the social isolation may mostly result from oversleeping — for example, they may choose to stay in bed instead of spending time with loved ones.

If you notice any signs and symptoms of seasonal affective disorder, it’s important to take them seriously. SAD isn’t just the “holiday blues”; it’s a health condition that requires treatment.

How is seasonal affective disorder treated? 

Seasonal affective disorder can’t be cured — but with the right treatment, its symptoms can be reduced. You can get personalized treatment for seasonal affective disorder and feel happier and more energetic all year round.

The most effective treatment for seasonal affective disorder is a combination of medication, light therapy, and psychotherapy.

Medication for seasonal depression

Antidepressant medications can help treat seasonal affective disorder. Medications like bupropion (Wellbutrin) are usually effective and safe for treating all types of depressive disorders, including SAD. However, they may not be a good fit for you if you have a history of bipolar disorder, a mood disorder that causes severe mood fluctuations.

Light therapy (phototherapy)

Light therapy is one of the most well-studied and effective treatments available for seasonal affective disorder. Light therapy uses a special light box that mimics natural light. Healthcare providers may instruct you to sit in front of the light when you get up to help regulate your circadian rhythm.

Although light therapy is usually safe, it’s important to get clear guidance from a mental health provider on using your lightbox. This can increase the odds that light therapy will be effective for you.


Several types of mental health therapy, including cognitive-behavioral therapy (CBT) with a behavioral therapist, can help with seasonal affective disorder. In fact, research shows that cognitive-behavioral therapy versus light therapy for SAD showed similar effectiveness. Therapy may be especially helpful for you if you deal with thinking or behavior patterns that make your depression symptoms worse.

For example, if you drink or use drugs to cope with the symptoms of SAD, then a therapist can help you examine that behavior and consider whether it’s truly helping you. If you have low self-esteem and have thoughts that you’re worthless, a therapist can help you replace those thoughts with more helpful ones.


There are other practices you can adopt that can help relieve some symptoms of SAD. These practices can’t replace formal treatment, but many find them useful.

  • Vitamin D supplements
  • Physical exercise
  • Spending more time outdoors
  • Connecting with loved ones
  • Eating a healthy diet
  • Following set bedtime and morning routines

Find a therapist to help with seasonal affective disorder on Klarity

Klarity makes finding a therapist for mental health care easy, affordable, and accessible. On Klarity, you can find a licensed mental health provider who can help you cope with seasonal depression. Whether you’re looking for an assessment, medication, and/or therapy services, get started and find a therapist on Klarity today.

FAQs about treatments and symptoms of seasonal affective disorder 

How do people cope with SAD?

There are many ways to deal with and effectively treat seasonal affective disorder. Most people benefit from a combination of light therapy, antidepressant medication, and talk therapy. You might also find that self-care practices, such as physical exercise and reaching out to loved ones, are helpful during this difficult time.

How does seasonal affective disorder differ from regular depression?

Seasonal affective disorder and major depression share the same symptoms. But seasonal depression comes and goes at the same time every year.

How does a healthcare professional diagnose seasonal affective disorder?

A healthcare professional diagnoses seasonal affective disorder if you have been experiencing symptoms for at least 2 years. They need to check to see if the depression symptoms come back at the same time for 2 or more years, which means that you won’t be diagnosed with SAD the first year you experience symptoms.

You will likely be diagnosed with and receive treatment for another mood disorder, like Major Depressive Disorder, until your provider can establish that your symptoms are seasonal.

The official diagnosis for seasonal affective disorder, according to the Diagnostic and Statistical Manual (DSM), is Major Depressive Disorder with Seasonal Pattern.

Can seasonal affective disorder affect individuals during seasons other than winter?

Yes. About 10% of people with seasonal affective disorder experience symptoms during the spring or summer months.

What is the toughest month for SAD?

Most people with seasonal affective disorder experience depression during the winter months. Your symptoms might start around October or when daylight savings ends. The months with fewer hours of sunlight tend to be the most difficult.

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All professional services are provided by independent private practices via the Klarity technology platform. Klarity Health, Inc. does not provide any medical services.
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PO Box 5098 Redwood City, CA 94063

100 Broadway Street, Redwood City CA, 94063

If you’re having an emergency or in emotional distress, here are some resources for immediate help: Emergency: Call 911. National Suicide Prevention Hotline: Call 988. Crisis Text Line: Text Home to 741-741
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