Shedding Light on Seasonal Affective Disorder

As the daylight hours get shorter and the cold weather blows in, some people begin to feel the “winter blues.” For some individuals, these feelings can become overwhelming and have a detrimental impact on daily living.

Seasonal affective disorder, or SAD, is a form of depression directly tied to the seasonality of weather and daylight changes. Symptoms normally begin when the weather turns colder and daylight decreases in the late fall or early winter and begins to lift when daylight increases and the weather turns warmer in the spring.

Though it’s very uncommon, some individuals experience the symptoms of SAD during the summer months.

[READ: Is My Depression Getting Worse?]

Who Gets SAD?

According to the American Psychiatric Association, seasonal affective disorder impacts around 5% of adults in the United States, affecting more women than men. (Children can be affected by SAD too.) It can last around 40% of the year, typically being the most challenging in January and February.

“Seasonal affective disorder has been linked to a biochemical imbalance in the brain, and people experience a shift in their internal clock, or circadian rhythm, that then causes them to be off-schedule with their daily life,” according to Dr. Krystal Lewis, a clinical psychologist with the National Institute of Mental Health in Bethesda, Maryland.

Other risk factors include:

Genetics. As with other forms of depression, experts believe that family history may play a role. People with SAD may be more likely to have relatives with SAD or a family history of depression or bipolar disorder.

Geography. Those living in colder climates to the north or south of the equator have a greater chance of experiencing SAD. This is due to less daytime light during the winter months.

[READ: Foods and Activities to Fight SAD.]

SAD Symptoms

When the weather starts changing, keep a close eye on a change in symptoms.

“Episodes of depression — seasonal or not — are diagnosed by the presence of significant sad mood or loss of interest or pleasure most of the day for at least two weeks, plus at least four other symptoms that persist during the same time frame and include significant disruptions in sleep, energy and appetite,” says Dr. James Murrough, associate professor of psychiatry and neuroscience at the Icahn School of Medicine at Mount Sinai in New York.

SAD may include some of these signs and symptoms:

— Changes in appetite resulting in either gaining or losing weight.

Depression most of the day, nearly every day.

— Feeling lethargic or agitated.

— Feeling hopeless or worthless.

— Having difficulty concentrating or making decisions.

— Loss of interest in activities you once enjoyed.

Sleep pattern changes, usually sleeping too much.

— Social withdrawal.

— Thoughts of suicide or death.

Diagnosing SAD

Like many mental health disorders, there is no blood test or brain scan that can detect SAD. Instead, like all forms of depression, SAD is diagnosed through a series of questions collected through a patient questionnaire. There are two tools — the Seasonal Pattern Assessment Questionnaire (SPAQ) and the Seasonal Health Questionnaire (SHQ) — that are widely used.

The SHQ was developed to be more sensitive and specific to identify symptoms of SAD. One study published in the journal BMJ found that the questionnaire was easily completed by patients and that it more precisely diagnosed SAD. “This newer tool is a step forward in helping to better diagnose people with SAD,” Lewis says.

[See: Apps to Support Your Mental Health]

Treating SAD

There are several different approaches to treating SAD. The mainstays of current SAD treatments include:

— Antidepressants.

— Bright light therapy.

— Cognitive behavioral therapy.

— Exercise.

— Healthy sleep hygiene.

As all three treatment options can take time to work, beginning your treatment plan proactively in early fall can be very effective in preventing the symptoms from occurring in patients that have a clear history of seasonal onset depression.

“Research has demonstrated that people can see improvements after just one week of light treatment, but it is recommended that the treatment be continued throughout the season, beginning in the fall,” Lewis says.

These options are typically used to treat SAD:

Antidepressant Medications

All types of depression, including SAD, are associated with changes in serotonin and other neurotransmitters. Your doctor may recommend using a selective serotonin reuptake inhibitor (SSRI) antidepressant or a different type of antidepressant called bupropion as part of your treatment plan.

Keep in mind that most antidepressants take a few weeks for the full benefits to begin, and it may be necessary to try more than one to find out which is best for you. Any side effects should be reported to your doctor and used to evaluate if a medication is right for your treatment plan.

Bright Light Therapy

Bright light therapy, also called phototherapy, has shown to be very effective for people dealing with SAD and is usually considered the first line of treatment. The decline in sunlight during the winter months can cause a drop in serotonin, a neurotransmitter that helps regulate mood, which can contribute to depression.

According to Murrough, “while the reason why bright light therapy is effective for SAD is not fully known, several randomized trials have provided support for its effectiveness. It is thought to help correct a misalignment between the sleep cycle and circadian rhythms in the body that is believed to contribute to the cause of SAD.”

Bright light therapy is typically done in the morning soon after waking. It involves sitting in front of a bright light therapy lamp (10,000 lux), which is about 20 times brighter than normal indoor lighting for anywhere between 20 to 45 minutes. A quality therapy lamp typically can be found for under $50, and a quick search online will yield many options.

Its purpose is to mimic the effects that sunlight has on your body,, which results in chemical changes in the brain boosting your mood. There is no need to worry about skin-damaging UV light as these therapy lamps filter it out. Talk to your doctor before using one as certain eye diseases or medications that increase light sensitivity need to be taken into consideration when deciding if this is the right treatment option for you.

Cognitive Behavioral Therapy

Commonly referred to as talk therapy, cognitive behavioral therapy aims to improve mental health by focusing on challenging and changing negative thoughts and behaviors, improving emotional regulation and developing personal coping strategies.

“Behavioral activation, a specific and important CBT skill, is a highly effective strategy for treating symptoms of depression. It encourages people to engage in pleasurable activities, even when one feels they don’t have the energy or desire to do so. It helps to break the cycle of low mood and energy,” Lewis says.


Exercising regularly will help provide your body with energy as well as a mood boost throughout the day. Bonus points for any physical activity outside,especially mid-day when the sun is at its highest, as more time outdoors can help supplement the natural decrease in sun exposure that occurs as winter progresses.

As daylight decreases and the cold weather increases, it’s a natural instinct to want to spend more time indoors with less physical activity and social interaction.Pushing back against that instinct is important however, as interacting with others and getting out of the house to do things you enjoy are both critical to mental health.

Healthy Sleep Hygiene

For individuals who are prone to SAD, making sleep a priority — both falling asleep and waking up at the same time every day — is critical.

“Ensure you are getting enough rest but not oversleeping and that you are eating foods that provide good nutrition, like foods with vitamin D,” Lewis says. “There is an association between vitamin D and serotonin activity. Due to the decrease in serotonin that can occur during seasonal transitions, it is important to increase foods with vitamin D and engage in activities that will help raise serotonin levels.”

More from U.S. News

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Shedding Light on Seasonal Affective Disorder originally appeared on

Update 08/18/22: This story was previously published at an earlier date and has been updated with new information.

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