What Is Seasonal Affective Disorder?
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Seasonal affective disorder (SAD) is more than just the “winter blues.” While holiday stress and cold winter months can affect anyone’s mood, for people with SAD, seasonal change causes more severe depression. In fact, about 5% of the U.S. population experiences SAD every year.
Experts believe that people develop SAD as a result of shorter daylight hours and less sunlight exposure. These changes can disrupt your body’s circadian rhythm and serotonin (your "happy hormone") levels. When this happens, most people with SAD experience symptoms like hopelessness, excessive sadness, social withdrawal, and oversleeping. While winter-pattern SAD is more common, people can experience SAD in the summertime, too.
Most people with SAD will notice an improvement in symptoms as the seasons change. Fortunately, there are treatments available, such as therapy and medication, that can help reduce symptoms more quickly.
Types of Seasonal Affective Disorder
There are two types of seasonal affective disorder, including:
Winter-pattern SAD: This is the most common type of SAD. People with winter-pattern SAD typically start experiencing symptoms in December. Symptoms usually subside in March. January and February tend to be the most challenging months for people with winter-pattern SAD.
Summer-pattern SAD: While less common, some people experience SAD during the summer months. For people with summer-pattern SAD, symptoms typically start in June and start to go away in September.
Symptoms
Regardless of whether you experience winter-pattern or summer-pattern SAD, you may experience the following symptoms:
Persistent feelings of sadness, emptiness, hopelessness, or worthlessness
Irritability
Loss of interest in activities you once enjoyed
Moving slowly
Physical aches and pains that are not occurring due to another health condition
But, SAD can also cause different symptoms depending on which season you're experiencing depression. Symptoms that are specific to seasonal patterns of SAD include:
Sleep disturbances: People with winter-pattern SAD may find themselves oversleeping, while people with summer-pattern are more likely to experience insomnia—the inability to go to sleep or stay asleep.
Changes in eating patterns and weight: In the wintertime, people with SAD might find themselves overeating and craving carbohydrates, which can sometimes lead to weight gain. People with summertime SAD may lose their appetite, leading to weight loss.
Social isolation: Winter-pattern SAD can cause people to isolate socially, or “hibernate.” In the summertime, people with SAD might experience social anxiety when spending time around others.
Causes
The winter season brings shorter days and therefore less sunlight. Winter-time SAD is thought to be caused by the effects of reduced sunlight exposure. Shorter days and less sunlight can affect the following factors and lead to depression symptoms:
Reduced serotonin: Some studies have shown that people with SAD have reduced levels of serotonin (known as the happy hormone) which helps regulate mood. Sunlight affects molecules that help maintain serotonin levels. Not getting the amount of serotonin your body needs can cause rapid changes in your mood.
Lower levels of vitamin D: Your body produces vitamin D when you are in the sun. Low levels of vitamin D are associated with a higher risk of depression and anxiety.
Increased melatonin: Melatonin is a hormone that helps maintain your sleep−wake cycle (also known as your circadian rhythm). SAD can cause altered levels of melatonin when the seasons change. People with winter-pattern SAD might produce too much melatonin in the colder months, leading to increased fatigue and oversleeping.
It’s important to note these theories still need more research, and there are even fewer studies available on summer-pattern SAD. Regardless, researchers generally agree that seasonal changes and shifting levels of sunlight can greatly affect your mood, sleep patterns, and daily rhythm, which for some can lead to increased levels of depression.
Risk Factors
The following factors can also increase your risk of experiencing SAD:
Being assigned female at birth
Being between the ages of 18 and 30 years old
Living farther away from the equator
Having an underlying mental health condition such as depression or bipolar disorder
Diagnosis
If you notice changes in your mood or overall quality of life when the seasons start to change, it can help to reach out to your primary care provider or a mental health professional for support. Your provider(s) may ask you to come in for an appointment or therapy session. During these appointments, they will likely screen you for depression and assess the following criteria:
Whether your depression has a seasonal pattern
If your symptoms are lasting three to five months at a time
If you've had seasonal changes in mood for at least two years in a row
Your provider may also ask you to fill out the Seasonal Pattern Assessment Questionnaire (SPAQ), which is the most common assessment for seasonal affective disorder. This questionnaire asks about factors like your mood, sleep quality, appetite, energy levels, and weight changes.
Additionally, your provider may also rule out any physical health conditions that can lead to depression symptoms. Some conditions that can mimic symptoms of SAD include hypothyroidism (an underactive thyroid) and hypoglycemia (low blood sugar levels).
Treatment
While symptoms of SAD often improve as the seasons change, treatment can help alleviate depression symptoms more quickly and make the winter or summer months more bearable for you. Your exact treatment plan will depend on the severity of your symptoms.
Related: 8 Ways to Cope With Seasonal Affective Disorder
Light Therapy
Light therapy is a popular treatment approach for people with winter-pattern SAD because it offers a solution for the most likely cause of your winter depression: a lack of sun exposure. Light therapy lamps, which shine at 10,000 lux (much brighter than everyday lamps) are available to purchase without a prescription. Experts recommend sitting in front of the bright light for about 30 to 45 minutes a day, starting in late fall and ending treatment in early spring for optimal results.
Psychotherapy
Like other types of depression, psychotherapy can help you better cope with symptoms of SAD and regulate your emotions. Cognitive behavioral therapy (CBT) for SAD is a specific type of therapy created to support people with seasonal affective disorder. This type of therapy focuses on challenging negative thoughts and motivating behavioral activation—a technique that encourages people to engage in healthy or joyful activities despite lacking motivation.
Antidepressants
If therapy isn't working for you, your provider may also recommend antidepressants, such as selective serotonin reuptake inhibitors (SSRIs). The SSRIs that are found to be most effective in treating SAD include:
Prozac (fluoxetine)
Zoloft (sertraline)
Vitamin D
With less sunlight exposure, your body produces less vitamin D. Some people may find that taking vitamin D supplements helps improve symptoms of SAD. But studies about this treatment have shown mixed results and more research is needed in this area. If you're interested in trying a vitamin D supplement, consult with your healthcare provider to see which supplement or combination of supplements is right for you.
How to Prevent SAD
In the U.S., SAD is more common in people who live farther north where there is less daylight in the wintertime. While moving closer to the equator may not be an option for everyone, there are other strategies you can use to make your symptoms more manageable.
For people with winter-pattern SAD, starting treatment in the fall can help prevent SAD symptoms as the days get shorter and colder. This could look like starting an antidepressant, attending therapy, or engaging in habits you plan to continue in the wintertime. For example, while exercise is known to reduce depression symptoms, it can be harder to find motivation in the winter. Getting into a gym routine or starting a fitness class that brings you joy can help encourage more frequent exercise in the winter months.
If you experience summer-pattern SAD, it could help to start meal-prepping in the spring or make a dietary plan full of foods you enjoy to help prevent unintentional weight loss that can occur with summer depression. You might also consider improving your sleep hygiene and environment, such as by getting black-out curtains or a white-noise machine to help you fall asleep during the summer.
Related Conditions
SAD often co-occurs with other mental health conditions, including:
Bipolar disorder (type 1 or 2)
Living With Seasonal Affective Disorder
With early treatment and planning, it is possible to live well with SAD. Taking medication, starting therapy, or making lifestyle changes in the fall (for winter SAD) or spring (for summer SAD) are some ways to make this condition more manageable. Additionally, reminding yourself that your depression won’t last forever can help you stay hopeful even in the darkest times. It’s also important to practice self-compassion and ask your loved ones for support and encouraging words during this time.
Frequently Asked Questions
Do vitamin D supplements help with SAD?
While low levels of vitamin D are common during the wintertime, it's unclear whether taking vitamin D supplements helps reduce symptoms of SAD. Current research shows mixed results.
What month does SAD start?
For people with winter-pattern SAD, symptoms will usually start in December. People with summer-pattern SAD will start to experience symptoms in June.
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