Seasonal Affective Disorder, or SAD, is a form of seasonal depression that impacts a person’s sleep patterns, mood, weight, and energy levels.

Between 4 to 6 percent of people experience winter depression, and 10 to 20 percent of people experience a mild form of seasonal affective disorder.

Below we’ll review the causes and symptoms of SAD, how it affects sleep, and treatment options.

What is Seasonal Affective Disorder?

For 90 percent of affected individuals, SAD strikes during the mid to late fall. The reduced sunlight during the winter months causes winter-onset SAD, and worsens depression symptoms for those who are already depressed. Besides depression, people with SAD also tend to experience hypersomnia, less energy, and poor mood.

The other 10 percent have summer-onset SAD, which comes on during the spring and brings with it summer depression, insomnia, and anxiety.

For either group, symptoms usually begin and end when the seasons change.

What are the symptoms of seasonal affective disorder?

SAD symptoms last for about 5 months, or for the length of the season. Both winter- and summer-onset SAD share the following symptoms:

  • Reduced energy
  • Depression and poor mood
  • Problems concentrating
  • Changes in appetite and body weight
  • Sleeping problems
  • Reduced interest in activities they formerly enjoyed

People with winter-onset SAD also typically experience increased irritability and sensitivity, an increased appetite for carbohydrates and consequent weight gain, lethargy, and hypersomnia. Meanwhile, people with summer-onset SAD will also experience increased anxiety, a reduced appetite and consequent weight loss, and insomnia.

SAD is different than the “winter blues” healthy individuals may feel on occasion when it’s cold and dark outside. SAD symptoms are persistent and extreme during the winter months. If a person has depression as well as SAD, their depression symptoms will significantly worsen during the SAD period. Likewise, bipolar individuals with SAD may experience increased depressive episodes during the winter and more mania during the summer.

In order to be diagnosed with SAD, the patient must experience symptoms at a higher frequency and intensity, exclusively during the winter or summer months.

Getting diagnosed with SAD

To receive a diagnosis of SAD, visit with a doctor or mental health professional. They may perform a psychological evaluation to assess the severity of your depression, or conduct a physical exam or lab tests to ensure your thyroid is functioning properly.

Prepare for your visit by asking yourself the following questions:

  • What are my symptoms? Am I feeling depressed or lethargic? Have my appetite or sleeping patterns changed?
  • What is the nature of my depression? When do I feel worse or best? Are there any triggers for those changes?
  • Are there other health issues or life events that could be contributing to my symptoms, such as the death of a loved one or a comorbid mental health condition?
  • What medications and supplements am I taking?

During your visit, consider asking your doctor the following questions:

  • Do my symptoms indicate I have SAD, or could there be another issue?
  • What can I do to improve my mood, weight, and sleep? Is there anything I should avoid doing or eating?
  • Are there medications I can take, or alternative treatments such as psychotherapy or light therapy?
  • Do you know of any resources I can use to find out more information or connect with others for support?

What causes seasonal affective disorder?

While the specific cause of SAD is unknown, scientists believe individuals with SAD experience a disruption to their circadian rhythm due to the changing amount of sunlight during the winter and summer months. Your circadian rhythm follows a nearly 24 hour cycle to regulate sleep and other physiological functions.

Serotonin and melatonin are two hormones responsible for regulating your mood and sleep patterns, and they both operate according to your circadian rhythm. Your levels of either hormone change depending on how your brain perceives sunlight, and they rise and fall inversely to each other. “Happiness hormone,” serotonin is high during the daytime when you need energy, while “sleep hormone” melatonin rises at night when you need to fall asleep.

When the sun goes down each evening, the pineal gland in your brain begins metabolizing serotonin into melatonin, preparing your body for sleep. But when there’s generally less sunlight overall, as in the winter months, it’s tougher for your pineal gland to do its job properly. Because there’s less sunlight, your brain produces melatonin for longer, making you sleepy earlier than normal and drowsier during the day. The change in sunlight also affects your serotonin levels, since you’re getting lower levels of vitamin D. Less vitamin D means lower serotonin levels, lower energy, and increased drowsiness. Individuals with winter-onset SAD experience extreme forms of these changes – longer melatonin production leads to hypersomnia, while lower serotonin levels results in depression.

With summer-onset SAD, individuals experience a reversal of these effects. The increased sunlight delays their melatonin production to the point of causing insomnia. They also experience heightened anxiety due to another hormone: cortisol. While cortisol levels drop during the winter, they raise during the summer. Increased levels of this “stress hormone” corresponds with the increased feelings of anxiety and insomnia experienced by individuals with summer depression.

sad cortisol levels wintersad cortisol levels summer
Source: Integrative Psychiatry

Risk factors for SAD

Scientists have identified traits that increase a person’s risk of having SAD. Women, younger people, individuals who already have depression or bipolar disorder, and people where SAD or other mood disorders run in their families are all likelier to have SAD.

People who live farther away from the equator are also more likely to experience SAD due to the varying extremes in sunlight during the summer or winter months. For example, 3 percent of Americans have SAD, but up to 9 percent of people in extreme northern or southern latitudes experience it.

In 2016, scientists identified a gene mutation among family members who have both seasonal depression as well as a faster-than-normal biological clock. Known as Familial Advanced Sleep Phase, these individuals tend to go to bed around 7:30 and wake up by 4:30. This further solidifies the connection between seasonal depression and a changing circadian clock.

Sleeping with SAD

One of the first warning signs of depression is sleep problems, and that holds true for seasonal depression like SAD as well. Because it is closely associated with winter depression (which affects the vast majority of people with SAD), hypersomnia is experienced by more people with SAD than insomnia (80 vs. 10 percent). Individuals with SAD are also likelier to be night owls and experience nightmares.

According to EEG recordings of their brain while they sleep, people with winter-onset SAD experience less sleep efficiency, less delta sleep, and increased time in REM sleep compared to themselves during the rest of the year as well as people with summer-onset SAD. Sleep efficiency refers to the amount of time spent asleep compared to the total amount of time spent in bed. The problem with lower sleep efficiency among people with SAD is that they aren’t getting the required amount of sleep they need, and the sleep they are getting isn’t as restful as it should be. For example, delta sleep restores the body, and people with SAD are spending less time in it at a time when sickness is high and you need your immune system at its best.  

Even more problematically, people with SAD aren’t good at gauging how well or how much they’re sleeping. They spend a lot of time in bed, and like insomniacs, they think they’re getting more sleep than they actually are. This can lead to them having problems getting diagnosed, and create more anxiety about why they feel so tired when they think they’re getting enough sleep.

Seasonal Affective Disorder Solutions; What Can Be Done?

Because of the seasonal nature of the disorder, most SAD symptoms go away naturally with the changing of the seasons. However, there is much that can be done in the meantime for individuals to feel and sleep better during their “off” season.

Lifestyle changes

  • Be thoughtful about how much natural sunlight you’re getting. If you have winter depression, spend more time outdoors, even when it’s overcast. When you’re not outdoors, do what you can to increase your exposure to natural sunlight. Sit by windows or leave the blinds open during the day. If you have summer depression, limit your exposure to bright light, especially at night. Wear sunglasses during the day, and block out the sun once it’s evening with blackout curtains to help facilitate melatonin production.
  • Exercise. Taking a walk outside during the day or exercising in the morning will boost your energy levels and help reset your circadian clock. Find an exercise buddy and choose something fun so it’s easier for you to stick to. Ideally, go for something aerobic – it’s been shown to elevate your serotonin.
  • Maintain a regular sleep schedule. Go to sleep and wake up at the same time every day to train your body to get sufficient sleep. If you’re especially tired during the day, you can nap, but limit it to a power nap of 20 minutes to avoid entering deep sleep and waking up more tired than before.
  • Go on vacation! Ideally, somewhere with the opposite season of where you live, so as to experience a reversal of your symptoms.
  • Manage your diet. Avoid over-indulging in carbohydrate-heavy foods – these contribute to the weight gain and lethargic symptoms of winter depression. If you’re experiencing a reduced appetite during the summertime, do what you can to make sure you’re still eating a healthy amount. Eat foods that promote healthy sleep. Here are a few recipes to help with seasonal depression:
    • For Breakfast: Blueberry Peach Smoothie – The blueberries, raspberries, and strawberries all help keep cortisol levels low, reducing your stress and anxiety.
    • For Lunch: Sausage, Kale, and Lentil Soup – The vitamin B12 in dark greens like kale boosts serotonin.
    • For Dinner: Fennel-Crusted Salmon on White Beans – The omega-3 fatty acids in the fish help regulate your mood, the magnesium in white beans reduces stress, and the fiber balances blood sugar and minimizes mood swings.
  • Try other mood-boosting activities. Art class, meditation, and massage all increase serotonin levels. The UK-based Seasonal Affective Disorder Association offers several more ideas in its Antidepressant Activities PDF.

Medication, therapy, and natural treatments

  • Aromatherapy has been shown to lift mood and aid sleep. Lavender in particular lowers your blood pressure and has a calming effect that alleviates insomnia and anxiety.
  • Natural supplements can also help manage sleep. Melatonin supplements are considered generally safe and help facilitate sleep, while also minimizing feelings of depression for people with SAD. Vitamin D supplements are another natural antidepressant, as is the herb St. John’s Wort. St. John’s Wort tea is a popular herbal treatment for depression in Europe.
  • Doctors may prescribe SSRIs and other antidepressant medications to help alleviate symptoms. Check with your doctor before taking any natural supplements in addition to your medication.
  • Cognitive behavioral therapy has proven extremely effective for both depression and insomnia. Over a series of sessions, therapists help individuals learn to recognize negative thought patterns and bad habits that make them feel depressed or keep them from falling asleep, and then replace them with more positive alternatives.

Light therapy and products

light therapy for sadLight therapy is the most recommended treatment for seasonal affective disorder. Individuals sit in front of special light boxes for 30 to 60 minutes in the morning or night, depending on whether they need to wake up or stay awake. The light boxes use 10,000-lux bright white fluorescent light bulbs to simulate sunlight. Individuals should have the box facing them but not look directly into the light to receive the intended effects.

Light boxes may have a “full spectrum” label. While full spectrum does not necessarily improve the effects of the therapy, it does ensure the light blocks out the UV rays which can be harmful

Light boxes come in a variety of forms to suit different lifestyles, applications, and style preferences.

  • If you’d like to use it during the day while you work, you can get a desk lamp light box like the Verilux HappyLight Liberty.
  • If you’d rather use it while you exercise, find one that specifies working at a sufficient range. Many light boxes work at 2 feet range, but you’ll potentially need something larger depending on your workout room. The light box might use reflective backing or include more light bulbs to deliver the required intensity at the farther distance.
  • Dawn simulator options, like this one from Philips, gradually light your bedroom to mimic the effect of sunrise.
  • If you don’t want your light box to interfere with your daily routine, consider a portable option that you can move around with you, like the Verilux HappyLight Liberty Personal, Portable Light Therapy Energy Lamp.
  • You can even wear your light therapy while you walk around, thanks to options like this visor from Feel Bright Light.
  • For the ultimate in portability, use a smartphone app. These rely on the phone’s blue light to deliver similar light therapy effects. The Blue Light Therapy iOS app offers a dawn simulator wake-up feature, as well as blue light therapy wallpaper that you can leave on while you work.