What Is Seasonal Affective Disorder (SAD)?
Medically reviewed by Lori Lawrenz, PsyD — By John M. Grohol, Psy.D. and Susanne Arthur — Updated on July 25, 2023
Seasonal affective disorder, or seasonal depression, is triggered by the changing seasons. It’s more common during fall and winter but can also occur in the summer.
It’s not uncommon for people to experience changes in mood — times when you feel sad and maybe not quite like yourself. Sometimes these mood changes coincide with the changing of the seasons, and sometimes they can be a sign of major depressive disorder (MDD) with a seasonal pattern, more commonly known as seasonal affective disorder or seasonal depression. This condition is common and especially prevalent in more northern regions where the days are shorter and the nights longer. Still, there are many ways to treat seasonal depression and many options that you can try on your own to help keep symptoms at bay.
Seasonal affective disorder (SAD) or seasonal depression are older terms for major depressive disorder (MDD) with seasonal patterns. However, since the older terms are more commonly known, they’re used throughout this article. We avoid using the abbreviation “SAD,” as it may be confused with social anxiety disorder. The condition is characterized by feelings of sadness and depression that occur with the changing seasons, most commonly in the fall or winter months when the temperatures begin to drop and the days grow shorter. The symptoms subside on their own as you transition out of the season that affects you. Because most people experience these shifts in mood during winter, it’s sometimes referred to as winter depression.
If your symptoms are less severe, the episode can be referred to as the “winter blues.” The official reference for this milder version is winter-type or winter-pattern subsyndromal seasonal affective disorder.
Growing research has found that in some countries, notably in North America, there’s a clear connection between latitude, or how far north or south you live, and the occurrence of seasonal depression. In other parts of the world, like parts of Europe, this connection is less clear. Overall, it’s estimated that between 1% and 10% of people experience seasonal depression. This can vary by country. Some research has found that 20% of people in the United Kingdom experience winter blues, while 2% experience winter depression. In Canada, the numbers are 15% for winter blues and 2%–6% for winter depression. Plus, in the United States, about 1% of people living in Florida experience seasonal depression, compared with 9% of Alaska’s population. Women are 4 times more likely to experience seasonal affective disorder than men, and the condition often begins when you’re between ages 18 and 30.
Though symptoms in winter are much more common, some people experience changes in mood at the onset of summer. This is known as summer-pattern or summer-type seasonal affective disorder, summer depression, or in its milder form, “summer blues.” Though statistics on the prevalence of summer depression are not as easily found as those for winter depression, it’s estimated that about 10% of people with seasonal depression experience it in the spring or summer. Plus, it can be observed that summer depression may be more common in some regions with warmer climates and possibly less access to air conditioning.
For example, an early study in the Netherlands found that only 0.1% of participants experienced the symptoms of summer depression, compared with 3% for winter depression. In comparison, a 2000 study of Chinese college students noted that summer depression was more common than winter depression, with 7.5%, compared with 5.6%. Similarly, in an early study conducted in Thailand, the prevalence of summer depression and summer blues was 6.19% and 8.25%, respectively, compared with 1.03% for winter depression. Only 97 people were included in the study.
We don’t know exactly what causes seasonal affective disorder. However, a few factors are thought to play a role. It’s possible that people who experience seasonal affective disorder have lower levels of serotonin, or the “feel good” hormone, which helps regulate your mood. Because sunlight exposure can impact serotonin levels in the body, winter depression may be brought on by lack of sunlight. However, summer depression may be triggered by heat, humidity, and too much light exposure, which can lead to an overproduction of melatonin, or the “sleepy” hormone. Too much melatonin in the body can affect your sleep-wake cycle. When seasonal changes in daylight exposure disrupt the levels of serotonin and melatonin in the body, it can impact your mood.
Seasonal depression is considered a type of MDD. Some of the signs and symptoms of seasonal depression are the same as those you might experience with other types of major depressive disorder. Winter and summer depression also have some specific symptoms, which will be outlined below. Keep in mind that not everyone experiences all of the symptoms listed.
Symptoms of major depression may include:
- feeling depressed nearly every day for most of the day
- losing interest in activities you enjoyed in the past
- changes in appetite or weight
- sleep problems
- feeling agitated or sluggish
- low energy
- experiencing a sense of hopelessness or worthlessness
- having difficulty concentrating
- experiencing frequent thoughts of death or suicide
Symptoms of winter depression
For winter depression, additional symptoms may include:
- oversleeping (hypersomnia)
- craving carbs
- weight gain
- social withdrawal or a desire to “hibernate”
Symptoms of summer depression
Specific symptoms of summer depression may include:
- trouble sleeping (insomnia)
- a lack of appetite that may lead to weight loss
- agitation and restlessness
If you’re experiencing symptoms of seasonal depression, reach out to a doctor or mental health professional to discuss your treatment options, which may involve a combination of therapy, medications, and coping strategies.
Strategies that may help with winter depression
Get as much natural light as possible
If you experience winter depression, increasing your daily exposure to as much natural light as possible can be helpful. You might find getting as much sunlight during the winter months as you can helpful. If you can, take a walk throughout the day or sit next to a south-facing window at your office, in a classroom, or at home. This will increase your sunlight exposure. Exercising next to a window or outdoors when possible is another activity that may help.
Consider light therapy
Light therapy can be an effective treatment for seasonal affective disorder. You can purchase specialized light therapy lighting boxes — sometimes called “SAD lamps” — for your home or office. It’s often recommended to sit in front of these lightboxes for about 30–60 minutes per day.
Light therapy is thought to improve seasonal depression. The increased exposure to light may:
- cause your brain to reduce the production of the hormone melatonin, which makes you sleepy
- increase the production of the hormone serotonin, which affects your mood
Though light therapy is recognized as a first-line treatment for seasonal affective disorder, the lamps can be a bit pricy. Some insurance plans may cover the cost of the light therapy box, especially if your healthcare professional recommends light therapy. If you have medical insurance, then checking with your insurance provider is a good idea. Also, inexpensive alternatives are available. You can replace commonly used light bulbs in your home with brighter full-spectrum (also known as broad-spectrum) light bulbs. The bulbs cost more than regular light bulbs, but their light is similar to natural sunlight.
Maintain your sleep schedule and routine
If you can, maintain your schedule and routine, which may help keep depression at bay. A regular pattern of sleep is most important to maintain. It may be helpful, for instance, to have your bedroom lights on a timer to turn on a half-hour before you wake. This may help in waking at a regular time every morning when it’s still dark outside in the winter months.
Exercising regularly may help boost your mood, which can be especially helpful if you have mild to moderate depression. For adults, aim for 150 minutes of moderate-intensity exercise a week, if you can. It’s important to pick an activity you enjoy, so you’re more likely to stick with it. If you can, pick an outdoor activity like walking briskly, running, skiing, or sledding, but any type of physical exercise can be helpful.
Eat a balanced diet
Overeating and, particularly, craving carbs are common symptoms of winter depression. High-sugar foods and carbs are known to give you a short boost of energy. There’s nothing wrong with enjoying a tasty treat from time to time, but try to eat a balanced diet rich in lean protein, fruits, and vegetables. These foods contain nutrients and compounds that may positively affect mood. For example, there’s some research on the potential effects of omega-3s in relieving the severity of depressive symptoms. Fatty fish is particularly rich in omega-3s. The fatty acids can also be found in plant foods like seeds and nuts, though the type of omega-3s in plant foods aren’t as active in your body.
To help you choose healthier foods, consider putting them in plain sight:
- Place a bowl of fruit in your kitchen where you can easily see it.
- Keep small containers with nuts or seeds by your work desk instead of high-carb sweets.
Strategies that may help with summer depression
Spend time in darkened rooms
Unlike winter depression, which seems to be triggered by a lack of sunlight, summer depression may be caused by too much sun exposure, which may affect your sleep-wake cycle. If you experience symptoms of summer depression, consider limiting your time outside. If you can, spend more time inside, preferably in darkened rooms. Still, it may be important to find a balance between seeking light exposure and avoiding it. Getting too little natural light may affect your mood.
Try to cool down
If heat seems to trigger your onset of summer depression, it may be important to find ways to stay cool. If you have one, using an air conditioning unit can be beneficial. Another option, if possible, is to consider going to locations with air conditioning running, such as supermarkets, malls, movie theaters, or libraries. You can also cool your home at night by opening windows if you don’t have air conditioning.
Regular exercise can help treat mild to moderate depression. It may also be an effective strategy for managing your summer depression. However, since too much sun exposure and heat could trigger your symptoms, you may want to opt for indoor activities, such as working out at a gym with air conditioning, swimming at an indoor pool, or trying a yoga class (just maybe not hot yoga).
What if these strategies don’t work?
If you start with coping strategies and techniques and they don’t seem to relieve your symptoms alone, your doctor may recommend psychotherapy or medications. Often, a combination of therapy, medication, and self-care strategies will be the most effective for treating seasonal affective disorder, similar to treating other types of depression. No matter what, don’t be afraid to speak with your healthcare professional about your symptoms. Together, you can work to find the right treatment options for you.