Humans, like most animals, are affected by sunlight or the lack of it, both physically and emotionally. But some people are affected much more than others. During the shorter, darker days of late fall and winter, especially in more northern regions, they may experience a type of clinical depression called seasonal affective disorder (SAD), also known as winter depression.
Instead of a unique diagnostic condition, SAD is considered to be a seasonally recurring subtype of depression. People with SAD typically experience symptoms of depression, such as a feeling of hopelessness for no evident reason, a loss of interest in people or things they normally enjoy, fatigue, difficulty concentrating, sleeping too much, and, in more severe cases, suicidal thoughts. In addition, they tend to eat more (especially carbs), which together with getting less physical activity, often leads to weight gain. Symptoms subside in the spring or early summer.
About 5 percent of American adults, on average, experience SAD, although some estimates run as high as 10 percent, depending on the criteria used and population studied (for instance, only about 1 percent of Floridians may have SAD, versus 10 percent of Alaskans). Women are more prone to SAD (as well as nonseasonal depression). Several genetic factors have been proposed to explain why SAD often runs in families and certain ethnic groups.
SAD can be mild to severe. Many more people have a milder, shorter-lasting form of SAD often called the “winter blues” (clinically known as subsyndromal SAD). For some people, mild SAD is distressing though manageable. For those with severe SAD, symptoms can be debilitating.
Even though SAD goes away on its own when the days get longer, it can last a full five months, with January and February tending to be the most difficult months. Fortunately, there are several ways to treat and possibly even prevent SAD, though there’s no one-size-fits-all approach. If you have symptoms like the ones mentioned above, it’s important to consult your doctor or a mental health professional. Don’t try to self-diagnose and self-treat.
SAD causes
Researchers have proposed several mechanisms to explain how light deprivation during winter may cause depression. Light deprivation can disrupt the body’s internal clock (circadian rhythm), which responds to environmental cues, notably light and darkness. With longer periods of darkness, the body’s production of melatonin increases; this hormone induces sleep and influences mood. Light deprivation also affects levels of the neurotransmitter serotonin, which helps regulate mood, energy, and appetite. Even variations in retinal sensitivity to light may play a role in some people.
A ‘happy box’ for SAD
Bright light therapy is often the first line of treatment for mild to moderate SAD. It attempts to replace the missing daylight and replicate its effects in the body—for instance by lowering melatonin production. Typically, you sit 16 to 24 inches from a special light box, positioned above eye level, first thing in the morning for about 20 to 30 minutes, with your eyes open but not looking directly at the light. The devices emit a controlled amount of white light, much brighter than ordinary lamps and with a filter to protect against ultraviolet rays that can be damaging to eyes and skin over the long term. The most effective light boxes emit 10,000 lux. (Lux is a unit of measurement of illumination.) By comparison, indoor home lighting is about 250 lux. You can read, do work, or even ride a stationary bike while using the light box.
Many people with SAD experience an antidepressant effect within one to four weeks, though some effects may be felt as soon as after a single session. Light therapy must be done every day, well into spring. If you know it can help you, you can start doing it as a preventive measure in early fall before SAD sets in. Not everyone benefits, however.
Light therapy is generally safe, but when used incorrectly, it may cause agitation, headaches, eyestrain, nausea, and insomnia. People with bipolar disorder or eye conditions should, in particular, seek medical advice before starting light therapy.
Another type of light therapy involves using a “dawn simulator,” which emits low levels of light in the morning that gradually increase to room level light over 30 to 90 minutes to awaken you and reset your body clock. Research on these devices has been more limited and inconclusive, however.
Because the dose and timing of light therapy should be tailored to your circadian rhythm and other factors, it’s a good idea to consult a mental health professional with expertise in SAD; they can also recommend a specific light box to buy. The devices vary in design and effectiveness and are not regulated by the FDA; very few have been tested in clinical trials. Underwriters Laboratories (UL) has approved some of them—but based on safety, not effectiveness. The Center for Environmental Therapeutics has developed a list of criteria for selecting a light box and provides other helpful advice and information about light therapy.
Antidepressants for severe SAD
The first line of treatment for severe SAD is a selective serotonin reuptake inhibitor (SSRI) antidepressant combined with bright light therapy. Another antidepressant, bupropion (Wellbutrin), has also been shown to be effective but without the weight gain and sexual dysfunction that an SSRI might cause. Other antidepressant side effects can include headache, diarrhea, anxiety, insomnia, ringing ears, and a fast heartbeat. Antidepressants can be either taken year-round or tapered and discontinued each spring or summer and restarted in early fall.
What about therapy or counseling?
Studies have found that short-term cognitive behavioral therapy (CBT) can help some people with SAD achieve acute remission and may even help prevent recurrences. The cognitive aspect of CBT identifies and reframes recurring negative thoughts, attitudes, and expectations that exacerbate symptoms, while the behavioral aspect identifies pleasurable behaviors and activities that may help you feel better.
In a study published in the American Journal of Psychiatry in 2016, 177 people with SAD were randomized to receive either CBT (two sessions a week) or light therapy (daily) for six weeks and then followed for the next two winters. In the first winter, outcomes for the participants in both groups were the same, but by the second winter after treatment, CBT was associated with fewer recurrences of depression compared to light therapy, even after adjusting for any current or new treatments. The results suggest that CBT “is a more effective means to reduce risk of recurrence than treating acute SAD with light therapy,” which, in contrast to CBT, has to be resumed every fall/winter to suppress symptoms.
What about vitamin D supplements or tanning beds for SAD?
Vitamin D is produced in the skin in response to ultraviolet (UV) rays from the sun. Because vitamin D blood levels are lower in the winter when there is less sunlight, it’s enticing to think that getting more vitamin D can reduce SAD symptoms. But studies testing vitamin D supplements for depression have been inconsistent or inconclusive. Tanning beds are not a good solution, either, since, unlike light boxes properly designed for SAD to filter UV rays, they can damage skin and eyes and increase the risk of skin cancer over the long term.
Can you just get more daily sunlight?
Maximizing your daylight exposure might help you feel better and may be all that’s needed for milder forms of seasonal depression. Try taking walks and exercising outside, even on cloudy days; making your house brighter; and sitting near windows on sunny days. Also, try to wake up and go to sleep at the same times each day and minimize exposure to blue light from computer monitors, TV screens, and electronic devices at least two hours before bedtime to help you get a good night’s sleep.
Some people experience spring-summer onset seasonal affective disorder, also called summer SAD or summer depression. As the name suggests, summer SAD begins in spring or summer and lasts until the fall or winter. Unlike fall-winter onset SAD, depression may be accompanied by insomnia and decreased sleep, a decreased appetite, and weight loss.
Summer SAD is much less common and not as well studied as winter depression. Thus, doctors don’t fully understand how and why the syndrome develops. Treatment is similar to that used for clinical depression, such as antidepressants. In addition, patients may be advised to limit time spent in natural daylight and use air conditioning to stay cool, especially in the evenings.
