Ascellus Blog

Understanding Seasonal Affective Disorder

December 29, 2021

Occurring during the winter months where sunlight is limited, seasonal affective disorder (SAD) affects approximately 5% of the U.S. adult population for roughly 40% of the year. Not merely “winter blues,” SAD is a medically-diagnosed mood disorder identified by a host of criteria. For those who experience SAD, the symptoms develop at approximately the same time each year, beginning as early as autumn when daylight hours shorten dramatically and continuing through the winter months. Although SAD affects some people during the summer months, it is less common.


Because SAD is a depressive disorder, its symptoms resemble those exhibited with major depression and may include any of the following.


  •     Frequent low mood
  •     Lack of interest in enjoyable activities
  •     Appetite or weight changes
  •     Sleep disturbance
  •     Lethargy or irritation
  •     Loss of energy
  •     Feelings of hopelessness or worthlessness
  •     Difficulty concentrating
  •     Recurring thoughts of death or suicide


In addition to these symptoms, the following symptoms are specifically associated with SAD:

  •     Oversleeping
  •     Overeating
  •     Weight gain
  •     Social disengagement


An individual diagnosed with SAD will have some, but not necessarily all, of these symptoms occurring frequently (more than they experience other depressive symptoms throughout the year) during the same months for at least two successive years.


Causes of SAD

While the causes of SAD are not completely understood, research indicates that serotonin, a neurotransmitter that stabilizes mood, is less active in people with SAD. Exposure to sunlight is known to increase serotonin production, and therefore, for those with SAD, serotonin levels decrease during the winter months.


Other findings suggest that people with SAD produce too much melatonin, which can disturb the body’s normal circadian rhythm and cause changes in mood and demeanor. While not thought to be wholly responsible for SAD, overproduction of melatonin can increase sleepiness, thereby decreasing energy and motivation.


Due to the effect of vitamin D on serotonin levels, vitamin D deficiency may intensify symptoms of SAD as well. The skin absorbs the sun’s ultraviolet B light and converts into vitamin D3. A study out of the University of Georgia finds that approximately two months after the sun’s ultraviolet rays peak in a given geographic area, people begin feeling the symptoms of SAD. Since it takes approximately eight weeks for the body to process UV radiation into vitamin D, the decreasing availability of sunlight following the peak intensity is likely to begin to negatively affect mood two months later. For this reason, vitamin D supplements have been dubbed the “sunshine vitamin.”


Treatment for SAD

There are several treatments that can offset the symptoms of SAD. The following lists the most effective therapies. Speaking with a healthcare provider will help you determine which one(s) are right for you.



Because SAD is a type of depression, it responds well to antidepressant medications designed to regulate serotonin levels. Classified as selective serotonin reuptake inhibitors (SSRIs), these medications are known to improve patients’ moods.


Vitamin D

Taking over-the-counter vitamin D supplements can help keep D3 levels consistent during the months when sunshine is at a minimum. However, there are also many foods that may be added to a regular diet to increase vitamin D levels, including:


Foods fortified with vitamin D

  •     Milk
  •     Orange juice
  •     Breakfast cereals


Foods naturally containing vitamin D

  •     Tuna
  •     Mackerel
  •     Salmon
  •     Beef liver
  •     Cheese
  •     Egg yolks


Light therapy

To replace the sunlight lost during the fall and winter months, light therapy is a popular treatment that is time-efficient and can be conveniently done at home. Between autumn and spring, begin every day by sitting under or near a bright light box (10,000 lux) for 30 to 45 minutes. Because the extremely bright bulb is designed to filter out harmful UV light, this treatment is safe. However, certain eye diseases and medications that may increase sunlight sensitivity preclude some people from using this therapy, so make sure to check with your doctor before using light therapy.


Cognitive behavioral therapy

Cognitive behavioral therapy specially used to treat symptoms of SAD is known as CBT-SAD. It helps people cope with their symptoms by correcting thought patterns that can cause the perpetuation of negative emotional responses. In just a few weeks, patients can learn to reframe unhelpful or harmful thoughts and decrease the detrimental effect of these thoughts on mood and behavior. Behavioral Activation is a key intervention in CBT-SAD aimed at teaching patients to identify indoor or outdoor activities, hobbies and tasks that they find enjoyable or fulfilling and then having them schedule them into their day to increase motivation and accountability and improve mood. Studies show that the positive effects of CBT are more robust in the long-term when compared to the benefits gained from light therapy.


Positive Activities

Understanding which symptoms of SAD most strongly affect you can help target an approach to combating their negative consequences. Remaining active is crucial to finding emotional balance throughout the winter months. The following list provides ideas to keep both the mind and body engaged.


  1.   Enjoy some outdoor sun: Even in the winter months, you can benefit from the sun’s rays. Taking a 15-30 minute walk in the early morning sunlight helps to maintain a healthy circadian rhythm.
  2.   Enjoy some indoor sun: Opening up blinds, shades and curtains and positioning yourself near a sunny window increases the home’s natural  light and can improve mood.
  3.   Start a winter hobby: With warm-weather hobbies on hold, engage in winter activities. Schedule a home improvement project or take up an outdoor activity, like snowshoeing, skiing or ice fishing.
  4.   Eat a balanced diet: While carbohydrate-filled comfort food is a cold-weather favorite, a physically and psychologically healthy diet should include small meals of fruit, vegetables, oatmeal, whole grain bread, brown rice and bananas. These foods improve serotonin levels, reduce mood fluctuation and increase energy.
  5.   Volunteer: Socializing and helping others reduces stress, anxiety and anger and is a great defense against depression.
  6.   Join a support group: Interacting with others who are facing similar problems helps people feel validated and decreases feelings of isolation.
  7.   Exercise regularly: This means 30-60 minutes most days of the week. Exercise increases the “feel-good” hormones, including serotonin, endorphins, dopamine and norepinephrine, and can help to lessen feelings of depression.


Healthy Strategies

Below is a list of Dos and Donts to foster healthy habits, productive goals and positive attitudes. Commitment to these guidelines can help equip you to more effectively combat the real or potential negative effects of seasonal depression.


Do ask for help                                                                   Don’t try to do everything on your own


Do talk to a friend, family member or therapist                 Don’t hold in stress and anxiety


Do accept yourself for who you are                                     Don’t think you have to be perfect


Do allow yourself time to relax                             Don’t think you have to be productive 24/7


Do set goals so your day has some structure      Don’t let procrastination control the day


Do go out with friends and enjoy activities              Don’t be attached to your phone 24/7


For those affected by SAD, the winter months are extremely challenging both mentally and physically, and as with any depressive disorder, complications can arise quickly. Therefore, it is important for those experiencing SAD to identify it early and seek treatment before symptoms worsen.

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