The symptoms of depression are very common. Some people experience these only at times of stress, while others may experience them regularly at certain times of the year. Seasonal affective disorder (SAD) is characterized by recurrent episodes of depression, usually in late fall and winter, alternating with periods of normal or high mood the rest of the year.
Whether SAD is a distinct mental illness or a specific type of major depressive disorder is a topic of debate in the scientific literature. Researchers at the National Institute of Mental Health (NIMH) first posited the condition as a response to decreased light, and pioneered the use of bright light to address the symptoms. It has been suggested that women are more likely to have this illness than men and that SAD is less likely in older individuals. SAD can also occur in children and adolescents, in which case the syndrome is usually first suspected by parents and teachers rather than the individual themselves.
While no specific gene has been shown to cause SAD, many people with this illness report at least one close relative with a psychiatric condition—most frequently a severe depressive disorder or substance abuse. Scientists have identified that a chemical within the brain (a neurotransmitter called serotonin) may not be functioning optimally in many patients with SAD. The role of hormones, specifically melatonin, and sleep-wake cycles (also called circadian rhythms) during the changing seasons is still being studied in people with SAD. Some studies have also shown that SAD is more common in people who live in northern latitudes (e.g., Canada and Alaska as opposed to California and Florida).
For all depressive episodes, it is important to understand the pattern of the condition, in other words, what stresses or triggers contribute to the depressive symptoms. In SAD, the seasonal variation in mood states is the key dimension to understand. Through recognition of the pattern of symptoms over time, developing a more targeted treatment plan is possible.
Symptoms of SAD usually begin in October or November and subside in March or April. Some patients begin to “slump” as early as August, while others remain well until January. Regardless of the time of onset, most patients don’t feel fully “back to normal” until early May. Depressions are usually mild to moderate, but they can be severe. Treatment planning needs to match the severity of the condition for the individual. Safety is the first consideration in all assessment of depression, as suicide can be a risk for more severe depressive symptoms.
Although some individuals do not necessarily show these symptoms, the classic characteristics of recurrent winter depression include oversleeping, daytime fatigue, carbohydrate craving and weight gain. Additionally, many people may experience other features of depression including decreased sexual interest, lethargy, hopelessness, suicidal thoughts, lack of interest in normal activities and decreased socialization.
In a minority of cases, symptoms occur in the summer rather than winter. During that period, the depression is more likely to be characterized by insomnia, decreased appetite, weight loss and agitation or anxiety. In still fewer cases, a patient may experience both winter and summer depressions, while feeling fine each fall and spring, around the equinoxes. Many people with SAD also report that their depression worsens or reappears whenever there is “less light around” (e.g., the weather is overcast at any time of the year, or if their indoor lighting is decreased).
Some people with bipolar disorder can also have seasonal changes in their mood and experience acute episodes in a recurrent fashion at different times of the year. It has been classically described that some people with bipolar disorder are more likely to experience depressive episodes in the fall/winter and manic episodes in spring/summer.
A person with any of these symptoms should feel comfortable asking their doctors about SAD. A full medical evaluation of a person who is experiencing these symptoms for the first time should include a thorough physical examination as well as blood (e.g., thyroid testing) and urine tests (e.g., pregnancy testing, drug screening). A medical evaluation is appropriate because SAD can often be misdiagnosed as hypothyroidism, infectious mononucleosis or other medical conditions.
Many people with SAD will find that their symptoms respond to a very specific treatment called light therapy. For people who are not severely depressed and are unable—or unwilling—to use antidepressant medications, light therapy may be the best initial treatment option.
Light therapy consists of regular, daily exposure to a “light box,” which artificially simulates high-intensity sunlight. Practically, this means that a person will spend approximately 30 minutes sitting in front of this device shortly after they awaken in the morning. Treatment usually continues from the time of year that a person’s symptoms begin, such as in fall, on a daily basis throughout the winter months. Because light boxes are created to provide a specific type of light, they are expensive and may not be covered by insurance. Unfortunately, having lots of lamps in one’s house and spending extra time outside is not as effective as this more expensive treatment.
Side effects of light therapy are uncommon and usually reversible when the intensity of light therapy is decreased. The most commonly experienced side effects include irritability, eyestrain, headaches, nausea and fatigue.
Scientific studies have shown light therapy to be very effective when compared to placebo and as effective as antidepressants in many cases of non-severe SAD. Light therapy may also work faster than antidepressants for some people with notable effects beginning with in a few days of starting treatment. Other people may find that it takes a few weeks for light therapy to work, which can also be the case for most people who take antidepressant medications. Although not explicitly recommended, some people may elect for treatment with both light therapy and antidepressant medications and find the combination of these treatments to be helpful.
Antidepressant medications have been found to be useful in treating people with SAD. Of the antidepressants, fluoxetine (Prozac) and bupropion (Wellbutrin) have been studied in the treatment of SAD and been shown to be effective. The U.S. Food and Drug Administration (FDA) has approved these medications for treatment of major depressive disorder but any person considering treatment with an antidepressant medication should discuss the benefits and risks of treatment with their doctors.
Some people may require treatment of their symptoms only for the period of the year in which they experience symptoms. Other people may elect for year-round treatment or prophylactic treatment that begins prior to the onset of the season in which their symptoms are most severe. This is yet another reason to discuss treatment options with one’s physicians. While not explicitly studied for the treatment of SAD, psychotherapy—specifically types of psychotherapy with documented clinical efficacy in the treatment of depression including cognitive behavioral therapy (CBT)—is likely a useful additional option for some people with SAD.
People with a history of bipolar disorder should be very cautious in approaching how they address depressive symptoms. Light therapy, like antidepressant therapy has been associated with increasing the risk of experiencing a manic episode. The specifics of this are beyond the scope of this review and again, should be discussed with one’s doctors.
Any person experiencing significant symptoms of depression should feel comfortable discussing their concerns with their doctors. Some primary care doctors (e.g., pediatricians and general practitioners) may be experienced in treating SAD and will feel comfortable treating this illness. Other doctors may want to refer people with SAD to a psychiatrist for treatment of this illness. This is more common in people with complex psychiatric illnesses or more severe symptoms. Before starting any treatment for SAD, a person should make sure to meet with their doctor to discuss the benefits and risks of treatment.
Friends and family members of people with SAD may be appropriately concerned for the well being of their loved one. The best way to be helpful to a person with SAD is for the people who care about them to be supportive in a non-judgmental fashion. This can include encouraging a person with symptoms to seek help for their condition.
Reviewed by Ken Duckworth, M.D., and Jacob L. Freedman, M.D., December 2012