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 called 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, which together with less physical activity, often leads to weight gain. Symptoms subside in the spring or early summer.
SAD can be mild to severe. Many more people have a milder, shorter-lasting form of SAD often called the “winter blues.” 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. Fortunately, there are several ways to treat SAD, notably light therapy and antidepressants, though there’s no one-size-fits-all treatment. 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.
What causes SAD?
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.
Treating mild SAD with light
Bright light therapy is often the first line of treatment for people with mild to moderate SAD, although it’s often combined with antidepressants. It attempts to replace the missing daylight and replicate its effects in the body. Typically, you sit 16 to 31 inches from a special light box, positioned above eye level, first thing in the morning for about 30 minutes. Fluorescent bulbs in the device emit a controlled amount of white light, much brighter than ordinary lamps, that shines into your eyes. The most effective light boxes emit 10,000 lux. (Lux is a unit of measurement that calculates illumination.) By comparison, indoor home lighting is about 250 lux.
You can read, do work, or even ride a stationary bike while using the box. Many people with SAD experience an antidepressant effect within one to four weeks. Light therapy must be done every day, well into spring. Bright light therapy is generally safe, but when used incorrectly, it may cause agitation, headaches, eyestrain, nausea, and insomnia.
Another type of light therapy involves using a dawn simulator. It emits low levels of light in the morning that gradually brighten to room level light over 30 to 90 minutes to awaken you and reset your body clock. They’re sometimes used in combination with a light box.
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.
Short-term cognitive behavioral therapy (CBT) is often combined with antidepressants and bright light therapy. CBT helps reframe recurring negative thoughts, attitudes, and expectations that exacerbate symptoms.
Soak up the sun
Maximizing your daylight exposure might help you feel better. Try taking walks outside, even on cloudy days; making your house brighter; and sitting near windows on bright days. Also, try to wake up and go to sleep at the same times each day, get plenty of aerobic exercise, 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.