When day trips to the beach, backyard BBQs, and lazy summer days come to an end, it’s only natural to feel a little sad. Suddenly, the hours of sunlight get shorter, and you find yourself leaving home and returning after school or work in total darkness.
Growing up in Canada, winter lasted a good nine months out of the year, and it was perfectly normal to still see snow falling in April. Where I come from, the winter blues were just an expected part of life. The short, dark days of winter always brought lower energy levels and mood, but as soon as spring blossoms appeared, the fog would fade away.
Many people experience the winter blues at some point in their lives, but what happens when those feelings don’t go away? For millions of Americans, the change of seasons negatively affects energy, weight, mood, and sleep.
Keep reading to learn about the symptoms of seasonal affective disorder, its close relationship with sleep, and some tips on how to sleep better in the winter months.
Seasonal affective disorder (SAD) is a type of recurring depression with a seasonal pattern. As summer turns into fall and winter, the temperature drops and the hours of sunlight decrease. For as many as 9% of the population, these changes trigger symptoms of depression that aren’t present at other times during the year.
SAD is different than major depression in that it comes and goes at roughly the same time every year. These symptoms can be so severe that they interfere with daily life and may even increase the risk of suicide.
A milder form of the disorder, known as subsyndromal seasonal affective disorder (S-SAD), is estimated to impact nearly 15% of the U.S. population. For this group of men, women, and even children, the winter blues may come and go but only cause small changes in things like mood, appetite, and energy.
Less often, a subtype of SAD causes symptoms during the seasonal transition into spring or early summer. While most people with the winter variation experience hypersomnolence (excessive sleep), those with the summer subtype are more prone to experience insomnia.
Researchers believe that both temperature and sunlight exposure may play a role in this disorder, with lower rates in sunny locales like Florida (1.4%) and higher rates in dark and cool places like Alaska (9.9%). Risk factors include being female, being younger, living farther from the equator, and having a family history of depression, bipolar disorder, or SAD.
The criteria for depression with a seasonal pattern, as set in the Diagnostic and Statistical Manual of Mental Disorders DSM-5 (otherwise known as the criteria accepted by doctors), is depression that starts and ends during a specific time every year with full remission during other seasons. The symptoms must last for at least two years with more seasonal episodes of depression than seasons without it over time.
For many others living in northern climates, the winter blahs are commonplace. While S-SAD can bring on small changes in mood and affect, the temporary symptoms are mild and can be managed with lifestyle changes like exercise, self-care, and meditation.
For those battling SAD, the symptoms are similar to major depression, affecting nearly every aspect of life. The two most common symptoms of SAD are low energy and a depressed mood, regardless of which variation occurs.
Those experiencing a winter seasonal pattern may also have the following symptoms:
On the other hand, those experiencing the less common summer variation may have these symptoms:
Individuals with depression, bipolar disorder, or other mental health disorders may also be affected by the changing seasons with a worsening of symptoms during the winter months. Bipolar disorder is characterized by alternating patterns of mania and depression, and many individuals with this disorder experience depressive lows during the winter months with manic highs during the summer.
Scientists are still trying to understand the complexities of mood changes over the winter months. They haven’t been able to pinpoint one distinct cause, but there are some biological explanations that they’ve been able to uncover. Blaming it all on the lack of sunshine may seem overly simple, but natural light exposure does play a huge role.
If you’ve ever taken an antidepressant, you may have heard the term “SSRI”. This stands for “Selective Serotonin Reuptake Inhibitors”. These medications work by increasing the amount of serotonin in the brain, thus helping to balance mood.
Serotonin is a neurotransmitter that's found in the brain and gut and is involved in regulating mood. Neurotransmitters are chemicals that act as messengers, relaying information from nerves to other nerves, muscles, or throughout the body.
Researchers have discovered that individuals with SAD may have difficulty regulating serotonin. SERT is a protein that transports serotonin, and when there are higher levels of this protein, less serotonin is available, leading to depression. Sunlight plays an important role in keeping SERT levels low, so when fall and winter come, serotonin levels drop.
One study found that people with SAD had 5% more SERT during the winter months than in the summer, which could explain their depressive moods.
There’s been a lot of talk about the hormone melatonin and the important role it plays in regulating the sleep-wake cycle, aka the circadian rhythm. To understand how light controls melatonin production, we need to jump into the brain to look at a tiny pea-sized structure known as the pineal gland.
The pineal gland is responsible for creating melatonin, the hormone that makes you feel tired. The suprachiasmatic nucleus (SCN) is a tiny part of the brain in the hypothalamus that tells the pineal gland when and how much melatonin to make. The SCN does this based on the information it receives from receptors in the eyes.
Natural sunlight helps to regulate this master alarm clock, relaying information about whether it’s day or night. Unfortunately, Americans spend over 90% of their time indoors, especially during the long and dark winter months.
Research has shown that individuals with seasonal affective disorder may produce excessive amounts of the hormone melatonin. This could explain why they feel excessively tired and sluggish during the winter months, often spending more time in bed.
Another downside to spending so much time indoors is that the skin misses out on the sun exposure it requires to produce Vitamin D. You’ve probably heard of this sunshine vitamin and that it also acts as a hormone in the body. Vitamin D has many different functions, and one is its involvement in serotonin activity.
You only need 5 to 30 minutes of sun exposure to the face, arms, legs, or back without sunscreen between 10 AM and 3 PM twice a week to get sufficient vitamin D, but most people aren’t even getting this. A detailed examination of National Health and Nutrition Examination Surveys from 2001 to 2004 discovered that 77% of the U.S. population is deficient in Vitamin D.
Many people living in northern climates have lower levels of vitamin D over the winter months, so much so that physicians often recommend a supplement between the months of November and March. Research has also discovered that people with SAD may produce less vitamin D, and a deficiency of this vitamin has been linked to depression.
The winter months bring less light exposure, which we’ve identified as a key factor in regulating the body’s master alarm clock. Increased melatonin and decreased serotonin can have a huge impact on the internal 24-hour sleep-wake clock.
People with SAD often have a circadian rhythm delay. Research has discovered that “the circadian signal that indicates a seasonal change in day length has been found to be timed differently, thus making it more difficult for their bodies to adjust.”
In one study, individuals with seasonal affective disorder had circadian rest-activity rhythms that were delayed by up to 70 minutes compared to healthy controls.
Another study examined whether the circadian pacemaker in patients with SAD signals a change in day length after the transition from winter to summer. They discovered that “patients with seasonal affective disorder generate a biological signal of change of season that is absent in healthy volunteers and that is similar to the signal that mammals use to regulate seasonal changes in their behavior.”
The problem with this signal in humans is that we don’t hibernate like other mammals. Healthy individuals don’t have this signal, so it could be part of the reason people with SAD react differently to the change in season.
Most people who experience SAD in the winter also report hypersomnolence or excessive sleep, whereas those who experience symptoms during the summer months tend to suffer from insomnia. Unfortunately, the extra time spent in bed doesn’t always equate with sufficient rest, with most individuals experiencing poor sleep quality.
While most individuals with winter-onset SAD experience excessive fatigue and sleep, there are some who have the opposite problem. Several studies in Northern countries have found that the darker winter months are associated with poor sleep.
One study compared sleep and mood in people living in two drastically different areas of the world where there is a great variation in sunlight throughout the seasons. In Ghana, where the duration of daylight remains constant, there was hardly any difference in sleep or mood throughout the winter months. In Norway, where there is a lack of daylight over several winter months, individuals reported insomnia, fatigue, and depression.
More and more research is looking at the close connection between mood and sleep. Many people suffering from depression report insomnia and other sleep disturbances, and scientists have identified that the part of the brain that regulates sleep is also closely tied to mood. A review done in 2013 found that the majority of those with mood disorders also have circadian rhythm disturbances affecting their sleep and wake cycles.
Another factor that may play a role in winter insomnia is the great amount of time spent indoors. Most of this time is spent in front of electronics like phones, computers, and televisions, all of which emit primarily blue light. This is one of many wavelengths of light that the sun naturally emits, but in our blue-lit 21st-century world, we’re being bombarded with round-the-clock blue light.
While some blue light is beneficial, too much of it could be negatively impacting our health. Research has shown that blue light directly inhibits our body’s melatonin flow, hurting our ability to fall asleep in addition to negatively impacting the quality of the sleep we get.
Twice a year every year, more than 70 countries and 1.6 billion people shift the clocks by one hour in a practice known as daylight savings. The practice that began in 1916 was designed to maximize exposure to daylight during the time that most people are active and outdoors.
Unfortunately, the practice of daylight savings causes disruptions to the circadian rhythm that have been shown to have multiple adverse effects. Many studies have found that daylight savings time transitions are associated with sleep disturbances, fatal car accidents, and increased heart attacks and strokes the day after the spring time change.
In a recent study, a team of international researchers looked at 185,419 Danish hospital intake records between 1995 to 2012 where there was a diagnosis of depression. These Danish scientists discovered that during the transition from summertime to standard time (known as “fall back”), there was an 11% increase in depressive episodes.
The researchers concluded that “the observed association is primarily related to the psychological distress associated with the sudden advancement of sunset from 6 PM to 5 PM, which marks the coming of winter and a long period of short days.” They believe that the majority of these individuals likely had suffered from seasonal depression in the past and that the sudden shift to less evening daylight served as an omen of the dark season ahead.
While the idea behind moving the clocks back in the fall is to provide more early morning sunlight, which should be beneficial for those with depression, the opposite may be true for those with SAD. Dr. Norman Rosenthal is a Psychiatrist and was one of the original doctors who first described seasonal affective disorder in 1984. He now speaks widely on the subject and is the best-selling author of a book entitled Winter Blues.
One of the more promising treatments for SAD is phototherapy, the use of artificial bright lights that emit full-spectrum rays similar in composition to sunlight. These small light boxes filter out UV rays and provide greater than 10,000 lux of cool-white fluorescent light that is 20 times greater than standard indoor lighting. They can be used for 20 to 60 minutes of morning therapy from early fall until spring to lower melatonin and increase mood-boosting chemicals and hormones.
It may be hard to believe that sitting in front of a light for a few minutes a day can battle depression, but plenty of research points to the fact that it works. To date, light therapy has been the most widely studied treatment for seasonal affective disorder. In a review of studies of light therapy, early morning treatment with an average dosage of 2,500 lux daily for one week was superior to placebo.
A meta-analysis of randomized control studies on light therapy to treat mood disorders found that bright-light treatment and dawn simulation for seasonal affective disorder was as effective as antidepressant medication. Dawn simulation is the use of a special alarm clock that gets progressively brighter, similar to the sunrise.
Research has found that the dosage of light therapy that is the most effective is 5,000 lux per day, which can be broken up into 2,500 lux for two hours or 10,000 lux for 30 minutes.
Photobiomodulation is another form of light therapy that uses non-ionizing forms of light, such as broadband light, lasers, and LEDs in the visible and near-infrared spectrum. One spectrum of light that has been well-studied for its multiple therapeutic benefits is red light.
NASA originally discovered the benefits of red LED wavelengths in 1993 when they were used to boost plant growth, but coincidentally, the scientists noticed that their skin lesions also began to heal faster. NASA continued to study these wavelengths to prevent bone and muscle loss in astronauts, increase cellular metabolism, reduce inflammation, and promote healing.
Studies have also found that photobiomodulation can alter brain chemistry, making it an effective treatment for anxiety and depression. Scientists have discovered that it works by increasing antioxidant and serotonin levels while simultaneously decreasing nitric oxide, cortisol, neuroinflammation, and oxidative stress.
The difference between these different forms of phototherapy comes down to spectrum. Light therapy is on the visible part of the light spectrum (between 400 nm to 480 nm), red light is also on the visible part of the light spectrum (between 630-700 nm), and near-infrared wavelengths fall into the invisible part of the light spectrum (between 700 and 1200 nm).
Source: “Effect of Wavelength and Beam Width on Penetration in Light-tissue Interaction Using Computational Methods“, Lasers in Medical Science
In 2018, one of the first studies of its kind was performed by some of the top mental health researchers. The Elated-2 Pilot Trial used transcranial (through the brain) near-infrared light (NIR) therapy to treat major depressive symptoms. The researchers concluded that “NIR light demonstrated antidepressant properties with a medium to large effect.”
A systematic review also looked at the use of red and near-infrared photobiomodulation for the treatment of depression. They reviewed multiple human and animal studies and discovered that this is a low-risk, inexpensive treatment with significant antidepressant effects.
There is a lot of research on the use of light therapy for depression, but the initial clinical research on photobiomodulation is also promising. So far, the studies have looked at major depression, not the seasonal variations. If you’re unsure about which type of light therapy to choose, it’s best to speak with your doctor about the research and your individual symptoms.
Some forms of depression come and go, so it can be hard to tell the difference between major depression and SAD. If your symptoms occur regularly every autumn or spring, lifting when the seasons change again, this could indicate seasonal depression. Depression is serious, and regardless of which type you have, it’s important to speak with your doctor about your symptoms and treatment options.
The biggest differentiating factor with SAD is that it comes and goes at the same time, year after year. Only a doctor or psychiatrist can determine whether you have seasonal affective disorder, so the first step is scheduling an appointment to discuss your symptoms. Keeping a journal about when you first noticed symptoms and their severity can help your doctor with making the proper diagnosis.
If your doctor decides to prescribe medication for your depression, you may wonder how it will impact sleep. While every person responds to medication differently, most antidepressants improve sleep over time. There may be an initial period of poor sleep as your body adjusts, but over time many people find that the quality of their sleep gets better.
With days getting shorter and darker, many people spend more time indoors staring at screens. This can disrupt hormone levels and the natural sleep-wake cycle. If you find that you’re having difficulty falling asleep or are waking up not feeling rested, talk to your doctor about your symptoms and the best type of treatment to improve them.
Many light-therapy devices can be purchased without a prescription, but it’s still important to speak with your doctor before starting therapy on your own. Your physician may be able to recommend a specific device or provide guidance on which type of light therapy is best for you. Always read the instructions before starting and follow the recommended guidelines on usage.
Winter blues or not, getting adequate sleep in this cold and dark season can be a challenge. If you feel tired and lethargic, you may not be sleeping enough or getting the restorative rest you need. Here are some tips on how to sleep better in the long, winter months:
Light therapy using light boxes or specially designed LED lights has been shown in research to be very effective for improving sleep. Most are small enough to sit on the counter and can be used for a few minutes each morning. Dawn simulators or wake-up lights are another great way to help reset your circadian rhythm, which in turn can help you sleep better.
Artificial lights can be helpful, but natural sunlight is best. Spending time outside in the sun every day is a great way to boost mood and to get vitamin D, which helps to battle depression. Similar to light therapy, this can help to regulate the circadian rhythm which improves mood and sleep.
Exercise has some amazing benefits for sleep. It triggers the release of endorphins and other chemicals that make you feel good, plus it can help you to sleep better at night (just be sure to work out earlier in the day). Bonus points if you can exercise outdoors in the natural sunlight!
Yoga, meditation, and prayer are all effective ways to calm the body and mind. In the morning, they can help you feel focused and more energized for the day. In the evening, they can clear the mind from all the worries of the day so you can focus on the most important task at hand – sleep.
One of the most underestimated yet effective ways to improve sleep is by sticking to a regular schedule when it comes to sleep and wake times. Going to bed and waking up at the same time every day helps to establish a pattern and balances the body’s internal master clock. Over time, maintaining this routine may help you to wake up feeling more alert and cut down on the time it takes to fall asleep at night.
Here are some good places to start:
If you suffer from the winter blahs, it may be tempting to just pack your bags and move south. Unfortunately, this type of major life change isn’t always feasible. Seasonal depression is a real disorder, and it’s important to seek treatment.
As we’ve seen in the research, it can impact every area of your life, including sleep. Thankfully, there are so many promising treatments that can help. If you’re struggling, remember that you’re not alone—find a friend, loved one, or trusted medical professional to speak with today so you can embark on your journey to feeling whole again.