Is It the Weather? Understanding Seasonal Affective Disorder (SAD)

By K Health
Medically reviewed checkmarkMedically reviewed
May 2, 2021

Everyone feels down sometimes. Feeling sad, lethargic, and moody can be normal every so often. But if you find yourself feeling depressed for weeks on end, or notice that these feelings intensify every winter, you might have seasonal affective disorder (SAD). SAD typically occurs during the winter season, but can also occur in the late spring or early summer and lift in the fall.

However, this particular type of SAD, sometimes called summer depression, is much less common. While it might be worrisome to experience seasonal depression, it is a well-studied condition that can respond well to treatment, including light therapy (phototherapy), psychotherapy, and medications.

What Is Seasonal Affective Disorder (SAD)

Seasonal affective disorder (SAD) is a type of depression that shows a seasonal pattern, appearing most often in the winter months, and less frequently during the summer months. Estimates range that between 1-5% of the U.S. population experiences SAD, with populations who live farther from the equator experiencing it at higher rates. Roughly 9% of the population in New England and Alaska experiences SAD, while only 1% of Floridians do. While anyone can be diagnosed with SAD, women make up nearly 40% more of the diagnoses, with young adults between 18-30 being the most susceptible age group.

Seasonal Affective Disorder Symptoms

To officially be diagnosed with SAD, you must display symptoms of major depression during the same time of year for at least two years. The symptoms of major depression include:

  • Feeling depressed for most of the day nearly every day for two weeks or more
  • Feeling lethargic or unmotivated, even during activities you used to enjoy
  • Feeling hopeless or worthless
  • Feeling fatigued and unmotivated
  • Insomnia
  • An increase or decrease in your appetite and/or weight
  • Difficulty concentrating

In addition to major depressive symptoms, there are distinct symptoms that appear to those experiencing SAD either in the winter or summer months. Often, symptoms are mild at the start of the season and become stronger as the season progresses.

Winter SAD Symptoms

  • Low energy and fatigue
  • A constant desire to sleep
  • Increased appetite (particularly for sweets and carbohydrates) and weight gain
  • Withdrawal from friends and social situations

Summer SAD Symptoms

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Causes of Seasonal Affective Disorder

There is no definitive reason why some people develop SAD and others don’t. However, scientists and doctors believe the following could play a role:

  • Low levels of the neurotransmitter serotonin in brain synapses: Serotonin affects mood, and a reduction of sunlight (which happens in late fall and winter), can cause a decrease in serotonin.
  • Circadian rhythm: Decreased sunlight in late fall and winter can disrupt your body’s internal clock, which regulates the sleep-wake cycle, as well as mood and appetite. In some, this disruption can cause grogginess, depression, and disorientation.
  • Melatonin: Changes in seasons can disrupt the balance of the body’s level of melatonin, a hormone that plays a role in your sleep-wake patterns and your mood. As sunlight decreases, the body increases melatonin production, and more melatonin can cause fatigue and lethargy, even when you’ve had enough sleep. Conversely, when sunlight increases in summer months, melatonin production decreases making it hard for some to fall asleep.

How Seasonal Affective Disorder Is Diagnosed

If you or your doctor suspects you have SAD, the following can help make a diagnosis:

  • Lab tests: Your doctor may order blood tests to determine if there is a biological cause behind how you’re feeling. Tests can include a complete blood count (CBC), a thyroid test, and a test to measure your vitamin D levels.
  • Physical exam: Your doctor may do a physical exam to determine if there are underlying physical issues causing you to feel depressed.
  • Psychological evaluation and family history: Your health care provider may ask about life events, family history, behavior, and thought patterns to better understand how you’re feeling. They may also ask you to fill out a written questionnaire about your mood and other aspects of your mental health.

Who Is at Risk for SAD?

Anyone can develop SAD, but certain factors may increase your likelihood of developing SAD. They include:

  • Gender: Most studies estimate that three out of four people with SAD are women. Scientists hypothesize that women’s fluctuating hormones can put them at a higher risk for developing SAD and other depression and anxiety disorders. It’s also possible that women seek treatment for SAD more often than men do. While more women seem to be affected by SAD, men with SAD report more intense symptoms.
  • Age: Most cases of winter SAD are diagnosed in young adults–usually between the ages 18-30.
  • Family history: If you have relatives who have SAD or other types of depression, you are more likely to develop the condition.
  • Other mental health conditions: If you have major depression, bipolar disorder, or other mental health conditions, you may be at increased risk of your symptoms worsening seasonally.
  • Living far from the equator: People living far from the equator have higher percentages of SAD.

Treatment Options

There are four primary treatments for SAD which can be used independently or in concert. Treatment options include:

  • Light therapy: Light therapy, also called phototherapy, imitates the effects of sunlight using daily exposure to bright, artificial light. For maximum effectiveness, sit within a few feet of a light box that supplies at least 10,000 lux of cool-white fluorescent light for at least 20-60 minutes first thing every morning from early fall until spring. Light therapy generally has no side effects, and is usually effective within a few days or weeks. Individuals with bipolar disorder should be cautious with phototherapy, as it may bring on a manic episode. It’s always recommended to consult with your doctor before using a light box for SAD. Tanning beds are not a suitable alternative to phototherapy, and can be harmful to your skin and eyes.
  • Medication: Selective serotonin reuptake inhibitors (SSRIs) make more serotonin available at the synapses in the brain, reducing symptoms of SAD. If you don’t respond well to SSRIs, you can also take bupropion, another type of antidepressant. If you have a pre-existing form of depression or bipolar disorder, your doctor may have other recommendations for medication.
  • Psychotherapy: Cognitive behavioral therapy (CBT) is the most effective therapy for SAD. In CBT, patients learn to identify harmful thoughts and behaviors and replace them with positive thoughts and actions. CBT also arms patients with tools for coping with symptoms of SAD, managing stress, and engaging in pleasurable activities to counter depression.
  • Vitamin D: Vitamin D on its own cannot successfully treat SAD. However, supplementing this important vitamin, often low in the blood of those suffering from SAD, can help reduce symptoms.


If you live in an area far from the equator, or are susceptible to depression, you may be unable to prevent SAD. However, there are some things you can do to help delay its onset, minimize its intensity, or for some, avoid it altogether. These include:

  • Get outside: It can be helpful to spend time outside every day, especially in the morning. Exposure to sunlight and fresh air are natural mood enhancers.
  • Phototherapy: Use a 10,000 lux light box preventatively. If you know you’re susceptible to SAD, you can begin phototherapy as soon as fall begins to prevent  the symptoms of winter SAD from starting
  • Eat well: Eating a diet of fresh fruits, vegetables, lean proteins, nuts, and seeds can help maintain your energy and keep you from feeling the lethargy of SAD. A balanced diet can also help you avoid the starch and sugar cravings that often accompany winter SAD.
  • Stay active: Exercising for at least 30 minutes a day can boost your natural feel-good hormones (endorphins) and keep symptoms of SAD at bay.
  • See your friends: Although there is a tendency in winter months to isolate and hibernate, socializing can minimize SAD symptoms and serve as a natural mood-booster.

What You Can Do at Home

Individuals diagnosed with SAD often need clinical treatment that includes phototherapy, psychotherapy, and medication. However, there are things you can do at home to support your professional treatment, or to cope with mild SAD symptoms. These are:

  • De-stress: Mind-body relaxation techniques such as meditation, guided meditation, yoga, tai chi, and chi gong can help mitigate the symptoms of SAD.
  • Let natural light in: During the day, keep your window shades open and sit near sunlit windows at home and work.
  • Spend time outdoors: Taking neighborhood walks, winter hikes, skiing, sledding, or even or having lunch outside can improve your mood. This is especially effective before noon when the sun is strongest.
  • Keep moving: Exercise, dance, vigorous yoga, and other types of exercise can relieve stress and boost your mood with endorphins.
  • Alternative medicine: Alternative remedies like herbal supplements, vitamins, acupuncture, and massage can help relieve SAD symptoms. Most alternative medicine have not been approved by the Food and Drug Administration (FDA), so consult with your health care provider to begin one or more of them.
  • Get away: If finances and life circumstances allow, a trip to a sunny, warm destination could help SAD symptoms. If you’re experiencing summer SAD, consider a trip to a cooler, shadier location.
  • Challenge negative thoughts: A hallmark of any form of depression (including SAD), is experiencing negative, unhelpful, and/or unrealistic negative beliefs.  Notice your own negative thoughts and challenge them by developing healthier and more balanced perspectives.

SAD can intensify symptoms for some people with bipolar disorder. When this happens, fall and winter can bring on depression, while spring and summer can instigate symptoms of mania or hypomania. Treatment recommendations for SAD differ for those with bipolar disorder, so consult with your health care provider if you have bipolar disorder and SAD.

When to See a Doctor

If feelings of depression, fatigue, and irritability persist for days or weeks, it’s a good idea to make an appointment with a health care provider, especially if you notice feeling this way around the same time each year. It’s normal to feel down sometimes, but if symptoms are preventing you from the activities in your day-to-day life, or if you have thoughts of harming yourself or others, a doctor could help craft a treatment plan to help you feel better soon.

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K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.

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