Seasonal Affective Disorder (SAD) – Causes, Signs and Symptoms

Seasonal Affective Disorder

Also called: SAD


Seasonal affective disorder (SAD) is a mood disorder marked by recurrent episodes of depression that occur during certain seasons of the year, particularly late fall and winter. In rare cases, patients may instead experience these symptoms during late spring and summer. Patients with SAD typically find that their depression lifts as soon as the troublesome season passes.

The exact cause of SAD is not fully understood. However, it appears that a decrease or absence of daylight plays a significant role in most cases. People who live in northern climates with longer nights and shorter days during the winter, or in an environment with frequent overcast skies, are especially at risk for SAD. The condition also affects women more often than men.

The depression associated with SAD tends to be mild to moderate in severity. Patients may experience symptoms that include daytime fatigue and lethargy, excessive sleep, weight gain and a strong desire for sugary or starchy foods. Patients who have summertime depression – also known as “reverse SAD” – may experience anxiety, decreased appetite, insomnia, irritability and weight loss.

Patients who feel depressed for any length of time or who feel that life has gradually become less pleasurable are urged to see a physician. Before diagnosing SAD, the physician will rule out other medical conditions that cause similar symptoms.

Light therapy is the chief treatment for SAD. In this therapy, patients sit before bright, fluorescent bulbs that are designed to concentrate the light on the lower half of the retina, an area of the eye that has photoreceptors involved in antidepressant response. Sessions typically last for 30 minutes or longer and are extremely effective for most patients. Antidepressants and psychotherapy are also used to treat SAD. Patients with mild forms of SAD may benefit from preventative measures such as taking an hour-long walk in bright winter sunlight, increasing the amount of light that enters the home, exercising regularly and performing other stress-reduction techniques.

The U.S. Food and Drug Administration recently approved the first medication for prevention of depressive episodes in patients with SAD.

About seasonal affective disorder

Seasonal affective disorder (SAD) is a mental health condition that causes recurrent episodes of depression at certain times of the year. People with SAD are most susceptible to depression during late fall and winter, when a decrease or absence of sunlight appears to negatively affect a person’s mood. Patients typically experience normal moods during spring and summer, when daylight is more abundant. 

Many people who live in cold winter climates experience temporary feelings of sadness, lethargy or similar emotions during this season. This is commonly known as “cabin fever” or the “winter blahs.” However, SAD is a condition that causes the patient to experience significant depression that interferes with their personal relationships, work performance and quality of life. Estimates have found that between 4 and 6 percent of people in the general population suffer from SAD, according to the American Academy of Family Physicians.

Some people with SAD may experience symptoms in the summer, with normal moods in the winter. This is called “summer SAD” or “reverse SAD.” Another rare form of SAD involves depression that occurs during the summer and winter, but lifts in the spring and fall. Although the exact cause of SAD remains unknown, changes in environmental light appear to be a major factor. The further north a person lives, the more severe the change in mood is likely to be. Persistent cloudiness also appears to trigger symptoms, as does decreased indoor lighting.

Risk factors and causes of SAD

The relationship between a lack of daylight and the depression associated with seasonal affective disorder (SAD) is not fully understood. However, SAD appears to be related to the way shifts in light change the seasonal activities of animals, including humans. Humans’ internal biological clocks – known as circadian rhythm – are altered during seasonal change, and in the winter months people may find that their biological clocks no longer correspond with their daily schedules. This may trigger depression.

In addition, the body hormone melatonin may play a role in the development of SAD. This hormone is produced at higher levels when a person is in a darkened environment – such as the shorter days and longer nights of winter – and it has been linked to higher rates of depression. Some experts also theorize that lack of sunlight leads to decreased production of serotonin, a neurotransmitter (brain chemical) that is involved in the regulation of mood. Heredity also appears to play a role in the development of SAD, as many people who have the condition also have a relative who has been diagnosed with a mental health disorder. Women are at particularly high risk for SAD, which tends to first appear in a patient’s 20s. However, men, adolescents and children can also experience SAD.

Signs and symptoms of SAD

Symptoms of seasonal affective disorder (SAD) typically fluctuate with the seasons. Many patients begin to experience depression in October or November, which may grow worse as the winter progresses. Depression tends to be mild to moderate, although some patients report more significant depression. Patients may experience several symptoms during this time, including:

  • Daytime fatigue and lethargy
  • Decreased interest in activities that are normally pleasurable such as sex (anhedonia)
  • Excessive sleep
  • Heaviness in the arms and legs
  • Lack of hope
  • Social withdrawal
  • Strong desire for foods that are sugary or starchy
  • Weight gain

Sometime in March or April, a patient’s mood typically begins to lift. By May, most patients have returned to their normal emotional state.

In rare cases, patients who have SAD may experience depression during the summer months. This is sometimes referred to as “reverse SAD.” Scientists believe this is a response to heat and humidity. Symptoms of reverse SAD include:

  • Anxiety
  • Decreased appetite
  • Insomnia
  • Irritability
  • Weight loss

Diagnosis methods for SAD

Patients who feel depressed for any length of time or who feel that life has gradually become less pleasurable are urged to see a physician. The physician will perform a complete physical examination and compile a thorough medical history of the patient. Several questions are likely to be asked of the patient, including:

  • What are some of the symptoms the patient is experiencing?

  • When did symptoms first occur?

  • Does the patient have a history of feeling depressed at certain times of the year?

  • Have seasonal symptoms been present for at least two consecutive years?

  • Does the patient spend a lot of time in the sun?

  • Is the lighting in the patient’s home inadequate?

  • Does depression typically lift during certain seasons of the year?

Before diagnosing SAD, the physician will rule out other medical conditions that may cause similar symptoms. These include viral infections (e.g., infectious mononucleosis), hypothyroidism (deficient production of thyroid hormone) and hypoglycemia (abnormally low levels of blood glucose).

Treatment options for SAD

Seasonal affective disorder (SAD) cannot be cured, but its symptoms can be treated effectively. Light therapy provided by bright, white, fluorescent bulbs is the primary treatment for SAD. These lights have color temperatures between 3,000 and 6,500 degrees Kelvin and are used in lamps surrounded by a box with a diffusing lens. This helps to filter out potentially harmful ultraviolet radiation. The lower color temperatures used in light therapy produce a soft, white light and the high color temperatures produce a colder light similar to the light in the sky.

Patients place the box on a tabletop with a stand that raises the light to eye level or above. This helps to both reduce glare and concentrate the light on the lower half of the retina, an area of the eye that has photoreceptors that appear to be involved in the antidepressant response. Patients should not stare directly into the light. In some cases, the light may be delivered through a visor device.

Sessions often are conducted in the morning and typically last for 30 minutes or more. Light therapy dosages are individualized for the patient, according to the intensity of light, the duration and the time of day of light exposure. Lights used in tanning beds are not effective for light therapy, as they fail to filter out ultraviolet rays.

Light therapy is often extremely effective. The lights used are 10 to 20 times brighter than typical indoor lights. Studies have shown that it helps reduce the production of the hormone melatonin, which has been linked to higher rates of depression. Between 50 and 80 percent of patients who undergo light therapy see their symptoms disappear completely, according to the National Alliance on Mental Illness (NAMI). In many cases, patients will begin to feel better after just a few days of light therapy, although it may take as long as a month in some cases. Treatments must be continued throughout the season that causes the symptoms.

Side effects associated with light therapy are uncommon and relatively minor. They may include irritability, eyestrain, headaches and nausea. However, patients with a history of bipolar disorder should approach light therapy with caution, as they may be at increased risk of experiencing altered mood states. Patients who take medications that make them sensitive to light also may not be good candidates for light therapy.

Antidepressants are also sometimes prescribed for patients with SAD and appear to be as effective as light therapy. In June 2006, the U.S. Food and Drug Administration (FDA) approved the use of bupropion HCL for the treatment of SAD. Another antidepressant that has shown to be effective in the treatment of the depressive disorder in clinical trials is fluoxetine. Patients who have a history of SAD may be put on antidepressant therapy shortly before the season that typically triggers symptoms, and discontinue the medication shortly after the season ends. Patients may not feel the benefits of antidepressants until between two to four weeks after they begin taking them.

The FDA has advised that antidepressants may increase the risk of suicidal thinking in some patients, particularly children and adolescents, and all people being treated with them should be monitored closely for unusual changes in behavior. New devices called dawn simulators are being studied as a potential treatment for SAD. Dawn simulators are used to provide a low level of light in the morning that gradually increases in intensity before a person wakes. Further research is necessary before the influence of an artificial dawn on SAD symptoms is understood.

Cases of SAD that involve summertime depression cannot be treated with light therapy, because it is believed that changes in mood are related to heat and humidity rather than a change of light. Air conditioning does not appear to provide effective relief from symptoms, although visits to cooler climates are beneficial in some cases. Antidepressants may also be prescribed for people with summer SAD.

Prevention methods for SAD

Patients who have mild symptoms of seasonal affective disorder (SAD) may find that certain actions can help ward off depression. Studies have found that people who take an hour-long walk in bright winter sunlight can significantly reduce their risk of SAD.

Patients can also try to boost the amount of light that enters their homes through opening blinds and adding skylights to their homes. Regular exercise and other stress-reduction techniques can help patients to feel more relaxed, making them less vulnerable to SAD.

Trips to sunny, warm-weather locales during winter – or to cool-weather places for those with reverse SAD – can help improve SAD symptoms.

In addition, the Food and Drug Administration recently approved the first medication (bupropion HCI extended-release tablets) for the prevention of depressive episodes in patients with SAD.

Children and SAD

In most cases, seasonal affective disorder (SAD) does not affect people until their young adult years. According to the American Psychiatric Association (APA), the average age of onset is 23. Some studies have indicated that somewhere between 1 and 6 percent of people ages 9 to 19 have SAD.

Parents and teachers are often the first to recognize symptoms of SAD in children. Children with SAD may begin to show signs of depression, withdraw from their friends and to experience a decline in academic performance due to an inability to concentrate. Other symptoms associated with childhood SAD include:

  • Crankiness or irritability
  • Temper tantrums during certain seasons
  • Tiredness

Parents who notice these symptoms and others related to SAD may want to have their child examined by a physician.

Children who are diagnosed with SAD will use many of the same treatment methods as adults, including light therapy, psychotherapy and antidepressant medications. However, parents should be aware that Food and Drug Administration (FDA) warnings regarding use of antidepressants are particularly focused on the use of these drugs in children. Studies have shown that antidepressant use may cause an increase in suicidal thoughts or behaviors in some children.

Parents can take several steps to help their children lower the risk of experiencing SAD. Parents are urged to encourage their children to get plenty of exercise, to spend time outdoors in sunlight (while the child wears proper sunscreen protection), to eat healthy foods and to get plenty of rest. Parents are also urged to help children with their homework and to remind their children that academic struggles related to an inability to concentrate should pass once the SAD is adequately treated.

Questions for your doctor regarding SAD

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions related to seasonal affective disorder (SAD):

  1. What signs should I look for that might indicate SAD?

  2. Is it possible that a condition other than SAD is causing my symptoms?

  3. Is light therapy a good option for me?

  4. How much time will my individual light therapy sessions last?

  5. How many months will my light therapy regimen last?

  6. Are there tips for getting the most out of my light therapy?

  7. Am I a good candidate for dawn simulation therapy?

  8. How far in advance of my “depressive season” should I begin taking antidepressants?

  9. What signs should I look for that I may be experiencing side effects?

  10. How long will it take for my treatments to begin working?

  11. What steps can I take to help prevent SAD?
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