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a couple sitting by the fire drinking out of mugs with a black cat on the floor

Shedding Light on Seasonal Affective Disorder

Roger Miller Clinical Psychologist Aviv Clinics by Roger Miller, PhD , Neuropsychologist
January 17, 2022
a couple sitting by the fire drinking out of mugs with a black cat on the floor

Shorter days, cooler temperatures, and less sunlight can trigger mood and cognition changes in some people. Called Seasonal Affective Disorder or SAD, this condition can be debilitating, but it is treatable.

SAD is a type of depression that emerges as seasons change. With winter’s limited hours of sunlight and the challenges to stay active outdoors, people who experience seasonal affective disorder can feel anxious, irritable, fatigued, sad, and have trouble sleeping, staying engaged, or thinking clearly. Some may even have thoughts of death and suicide, lose their appetites, and experience weight gain or loss.

Symptoms typically begin when the days get shorter in the fall and winter. Many describe it as winter blues. Symptoms subside with the onset of spring and more daylight hours.

Who is affected?

Millions of people likely suffer from SAD every year, but some may not even realize their depression is linked to SAD, according to the National Institute of Mental Health. More women than men are affected, and it’s more common in people living farther north, where there are fewer sunny days in the winter.

“SAD sometimes runs in families. SAD is more common in people who have relatives with other mental illnesses, such as major depression or schizophrenia.” – National Institute of Mental Health

The condition can also be more common in people with major depressive disorder or bipolar disorder. Those with attention-deficit/hyperactivity disorder, an anxiety disorder, or an eating disorder are also more prone to developing SAD. It can also impact more than one family member.

What causes SAD?

Sunlight helps the body produce vitamin D, which is essential for maintaining the chemical (neurotransmitter) serotonin in the brain. Insufficient levels of serotonin can negatively affect mood and cognition because the brain is not firing properly. If the neurotransmitters are not firing, nothing works well, including memory, learning, and concentration.

When the season shifts and days become shorter, there is less sunlight available and less opportunity to produce the much-needed vitamin D.

Shorter days also can interfere with the circadian rhythm or sleep-wake cycle, resulting in an overproduction of melatonin, a hormone critical for maintaining the body’s normal daily rhythm. Too much melatonin can cause sleepiness and reduce energy.

Shorter days and less sunlight not only rob the body of the critical vitamin D it needs, but it also keeps people indoors more and, potentially, less active. The lack of physical activity and social interaction because of being indoors exacerbates symptoms of seasonal affective disorder. Neither the brain nor the body has much energy, leading to increased fatigue and worsening SAD symptoms.

Without connecting with others or participating in enjoyable activities, people are more apt to experience loneliness and isolation, which ultimately can affect mood and mental health.

Eating poorly can also intensify symptoms. Wintertime holidays like Christmas and New Year’s Eve are celebrated with hefty feasts that often include sugar-laden foods, lower-quality carbohydrates, and highly saturated fatty foods, which can create inflammation in the body. Studies have shown that sugary drinks, refined carbs, foods high in trans fats, highly processed foods, artificial sweeteners, and alcohol can increase inflammation and impact memory and learning.

How is it treated?

SAD is mainly treated with light therapy. Other methods that may be used in conjunction with light therapy include talk therapy, vitamin D supplementation, and antidepressant medications.

  • Light therapy. To make up for the loss of sunlight, a SAD sufferer can soak up intense light using a light box, which provides up to 20 times more light than ordinary indoor light without the damaging UV rays associated with natural sunlight. To reap the most benefit, the person should sit 30 to 45 minutes each morning in front of the box. Light therapy is not recommended for someone with bipolar disorder because the intense illumination can lead to a manic episode.
  • Talk therapy. Because some people associate winter with negative thoughts, psychotherapy may be beneficial to help with restructured thinking. Talk therapy works well in conjunction with light therapy.
  • Medications. For some people, antidepressants may be necessary. Medications called selective serotonin reuptake inhibitors (SSRIs) are used to treat SAD when symptoms occur.
  • Vitamin D supplements. A lack of sunlight will result in a vitamin D deficiency. A vitamin D deficiency causes fatigue, bone pain, muscle weakness, and mood changes like depression. Although sunlight is the best and preferred source for vitamin D, light therapy, food, and supplements are alternative sources.

When to seek help

If symptoms are interfering with quality of life—poor sleep, loss of interest in activities, or self-isolation—it’s time to talk to your doctor.

Can the symptoms of seasonal affective disorder be prevented? All of the symptoms may not be entirely preventable, but there are things you can do to reduce the severity of how you feel.

  • Begin light therapy earlier, before the onset of symptoms.
  • Take advantage of daylight hours to exercise outdoors.
  • Be socially active even when you feel like you would rather stay indoors.
  • Choose brain-beneficial foods that promote good mental health.
  • Maintain your sleep routine and keep the same cycle you are used to.

The bottom line

The seasonal doldrums may affect those sensitive to the shorter days and limited sunlight. Maintain your routine and plan ahead in terms of your social environment, healthy eating, and physical activity. Light therapy, vitamin D supplements, medication, and talk therapy may also be recommended by your doctor.


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