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  • Seasonal affective disorder (SAD) is linked to the lower sunlight exposure that typically occurs in winter months; for instance, SAD affects only 1 percent of Floridians compared to 9 percent of Alaskans
  • People with SAD may overproduce melatonin, such that the increased darkness that comes along with winter leads to feelings of sleepiness and lethargy, or melatonin production may be phase-delayed, which means it’s produced at the wrong time
  • Full-spectrum light therapy (or sunlight exposure), Emotional Freedom Techniques, exercise and cognitive behavioral therapy are among the most effective SAD treatments

By Dr. Mercola

Seasonal affective disorder (SAD) is a form of depression that occurs seasonally, typically ramping up in the fall and winter months and disappearing come spring (although it may occur during other seasons as well, albeit less often). It’s quite common for people to notice changes in their mood, energy levels and food cravings when the weather turns colder and the days get shorter, but this slump, known as “winter blues,” is different from true SAD.

In the case of SAD, symptoms are so severe that they interfere with daily life. “I feel myself wanting to cry for no reason; I overreact extensively and am extremely irritable,” one SAD sufferer told NBC News.1 “There are days where I cannot bring myself to get out of bed or function.”

Common SAD symptoms include oversleeping, intense carbohydrate cravings, overeating and weight gain. Some people also have trouble concentrating and withdraw socially,2 preferring to “hibernate” indoors instead of carrying on with their normal day-to-day activities.

Dr. Norman Rosenthal, clinical professor of psychiatry at Georgetown University School of Medicine, was the first to describe SAD, writing in a 1984 journal article that the “depressions were generally characterized by hypersomnia, overeating and carbohydrate craving, and seemed to respond to changes in climate and latitude.”3 Indeed, rates of SAD vary depending on location, with people living farthest from the equator in northern latitudes being most susceptible.

In the U.S., for instance, according to a review published in Depression Research and Treatment, SAD affects only 1 percent of Floridians compared to 9 percent of Alaskans.4 Women are also at increased risk, with SAD being diagnosed four times more often in women than men. Young adults also seem to be disproportionately affected (SAD typically begins between the ages of 18 and 30 years),5 and this could be due to links to ancient ancestors. Professor Robert Levitan of the University of Toronto told The Guardian:6

“Because it affects such a large proportion of the population in a mild to moderate form, a lot of people in the field do feel that SAD is a remnant from our past, relating to energy conservation. Ten thousand years ago, during the ice age, this biological tendency to slow down during the wintertime was useful, especially for women of reproductive age because pregnancy is very energy-intensive.

But now we have a 24-hour society, we’re expected to be active all the time and it’s a nuisance. However, as to why a small proportion of people experience it so severely that it’s completely disabling, we don’t know.”

Why Shorter Days, Less Sunlight May Lead to SAD

A whole host of physiological processes are directed by your body’s circadian rhythm, which is calibrated by exposure to natural sunlight and darkness. Regular sunlight exposure is a crucial part of this equation. Many have become familiar with its importance for optimizing your vitamin D levels — and there is research showing that not only is SAD more common in people with low vitamin D levels, but improving levels improves SAD symptoms.7

However, sunlight’s role in this condition goes far beyond vitamin D. For instance, sunlight helps to keep levels of the protein SERT low. As a key player in transporting the neurotransmitter serotonin, known to play a role in mood, low levels are a good thing, as higher SERT levels are linked to lower serotonin activity and increased depression. According to the Depression Research and Treatment review:8

“In one study, people with SAD had 5 percent more SERT, a protein that assists with serotonin transport, in the winter months than in summer9 … Throughout the summer, sunlight generally keeps SERT levels naturally low. But as sunlight diminishes in the fall, a corresponding decrease in serotonin activity also occurs.”

The SAD-Melatonin Connection

Your master biological clock resides inside the suprachiasmatic nucleus (SCN) of your brain, which is part of your hypothalamus. Based on signals of light and darkness, your SCN tells your pineal gland when it’s time to secrete melatonin and when to turn it off. One of melatonin’s primary roles is regulating your body’s circadian rhythm. When it gets dark, your brain starts secreting melatonin (typically around 9 or 10 p.m.), which makes you sleepy.

Levels typically stay elevated for about 12 hours; then, as the sun rises, your pineal gland reduces your production and the levels in your blood decrease until they’re hardly measurable at all. People with SAD may overproduce melatonin, such that the increased darkness that comes along with winter leads to feelings of sleepiness and lethargy, or melatonin production may be phase-delayed, which means it’s produced at the wrong time.10

The combination of low serotonin and excess melatonin may prove to be especially problematic for circadian rhythms, and there’s evidence that, for people with SAD, “the circadian signal that indicates a seasonal change in day length has been found to be timed differently, thus making it more difficult for their bodies to adjust.”11

It’s also been proposed that seasonal changes in diet could play a role in SAD, and research has found that vegetarians are four times more likely to suffer from SAD than non-vegetarians.12 Vegetarians have also been found to be twice as likely to suffer from nonseasonal depression,13 which suggests that nutrient deficiencies may be involved in both.

Exposure to Sunlight — Full-Spectrum Light — Is Crucial

Full-spectrum light therapy is often recommended for the treatment of SAD. Light therapy alone and placebo were both more effective than the antidepressant Prozac, even for the treatment of moderate to severe depression, in an eight-week-long study.14

Further, in a study of patients with bipolar disorder, who have recurrent major depression, bright white light therapy was also effective in boosting mood, with 68 percent achieving a normal mood after four to six weeks of treatment compared to 22 percent of those who received a placebo treatment.15

The idea is to try to simulate exposure to natural sunlight during times of the year when it may not be available. Researchers explained that sitting in front of a light box, first thing in the morning, daily from early fall until spring, may be necessary to help relieve SAD symptoms. Further, if you know that SAD symptoms tend to come back for you every winter, you may want to start light therapy earlier, such as during late summer:16

“In the Scandinavian countries, light rooms, where light is indirect and evenly distributed, are available. Typically light boxes filter out ultraviolet rays and require 20 to 60 minutes of exposure to 10,000 lux of cool-white fluorescent light daily during fall and winter. This is about 20 times as great as ordinary indoor lighting.”

It’s exposure to the full spectrum of light that’s so important, as exposure to only one type of light can be counterproductive. Going outside around sunrise, for instance, would provide exposure to full-spectrum light in a form superior to virtually any light box — the real, full-spectrum light from the sun is ideal.

Exposure to sunlight is also important, not only because it will help optimize your vitamin D level,17 but also due to other mechanisms, like regulating your circadian rhythm and production of serotonin, which is released in response to sunlight exposure.

Emotional Freedom Techniques (EFT), Cognitive Behavioral Therapy May Also Improve SAD

Total playlist length: 28:08

Energy psychology uses a form of psychological acupressure, based on the same energy meridians used in traditional acupuncture to treat physical and emotional ailments for over 5,000 years, but without the invasiveness of needles. One such form is the Emotional Freedom Techniques (EFT), which has proven effectiveness in improving mental health, including depression.

While I have long recognized the value of EFT, it’s finally starting to get some mainstream attention. Speaking to CBS News, Pittsburgh area therapist Joan Kaylor stated, “By tapping on these points, this can have an effect on Seasonal Affective Disorder by removing the sadness, by removing both the emotional component, as well as any physical sensations.”18

Another option is cognitive behavioral therapy (CBT), which helps you to modify behaviors, thoughts and emotions that may be affecting your mental health and happiness. It’s been shown to help people with SAD. Research published in the American Journal of Psychiatry found that CBT works the same as light therapy in improving SAD symptoms,19 and you may want to consider a combination of the two. Rosenthal told NBC News:20

“Several controlled studies have shown that CBT can be extremely valuable not only in helping people who have SAD, but in preventing subsequent episodes. SAD is an illness where your behavior will have a major play.

Also if you don’t know what’s going on, you begin to blame yourself and think you’re a failure. CBT can correct dysfunctional behaviors that may [arise from SAD] like lying in bed late with covers over your head, which is the worst thing you can do as you’re depriving yourself of natural light when it is its most effective: in the morning.”

It’s worth noting, too, that winter is a natural time for your body to slow down somewhat. While this can be difficult when your work and personal life dictate otherwise, allowing yourself time to overwinter may ultimately help you to respect your body’s circadian rhythm and recharge.21 That being said, this doesn’t mean you should plant yourself on the couch for the winter and not venture outdoors. The opposite — staying active and getting outside — is among the best “cures” for SAD.

Stay Active and Get Outdoors to Fight SAD Symptoms

Exercise is another well-known tool for improving your mental health. In my 2008 interview with Dr. James Gordon, a world-renowned expert in using mind-body medicine to heal depression, he stated that physical exercise is at least as good as antidepressants for helping people who are depressed, in part because it increases serotonin in your brain and in part because it increases brain cells in your hippocampus, which are sometimes reduced in people with depression. He’s far from the only one to come to this conclusion.

In 2013, a meta-analysis published in the Cochrane Database of Systematic Reviews found that exercise is moderately more effective than a control intervention, which in some cases was pharmaceuticals, for reducing symptoms of depression.22 Separate research published in the American Journal of Preventive Medicine found that aerobic exercise “at a dose consistent with public health recommendations” is an effective treatment for mild to moderate depression.23

Exercise has even been found to increase your resilience to stress, which may make enduring those cold winter days more tolerable.24If you can, do your workouts outdoors so you can get some sunlight exposure along with them. As Dr. Meir Kryger, professor of medicine at Yale School of Medicine, told NBC News, “The worst thing you can do is stay indoors and not be exposed to natural sunlight at all.” As an alternative, Rosenthal suggests doing your workout in front of your full-spectrum light box.25

Focus on Self-Care, Stress Relief and Healthy Lifestyle to Reduce SAD

In many cases, leading a healthy lifestyle, one that helps you to relieve stress and provides the nutrients your body needs physically, will help you to continue functioning with SAD. For example, Rosenthal has said that “Transcendental Meditation (TM), other forms of mindfulness, yoga, walking and exercise that is personally enjoyable were beneficial.”26 Even taking a vacation to sunny destination during the winter can help, if possible.

Tryptophan is another tool, one that’s been shown to be equally effective to light therapy in treating SAD.27 Your body produces 5-HTP (5-hydroxytryptophan) from the amino acid tryptophan (found in foods like poultry, eggs and cheese). However, eating tryptophan-rich foods is not likely to significantly increase your 5-HTP levels, so 5-HTP supplements (which are made from extracts of the seeds of the African tree Griffonia simplicifolia) are sometimes used.

The chemical 5-HTP works in your brain and central nervous system by promoting the production of the neurotransmitter serotonin and thereby may help boost mood. In addition, the following three factors will help “anchor” your biological rhythm, which will promote body clock synchronization and optimal health.

  • Get bright daylight exposure, ideally around solar noon, for at least a half-hour or more each day. This will “anchor” your circadian rhythm and make it less prone to drifting if you’re exposed to light later in the evening.
  • Then, in the evening, put on blue-blocking glasses and/or dim environmental lights and avoid the blue light wavelength (this includes LED light bulbs, TVs and most electronic gadgets)
  • When it’s time to go to sleep, make sure your bedroom is pitch black. I recommend installing blackout shades for this purpose or using a sleep mask. Also keep in mind that digital alarm clocks with blue light displays could have a detrimental effect, so if you have to have an LED clock, opt for one with a red display, and set it on its dimmest setting. You can also try a dawn-simulating clock that imitates a natural sunrise in the morning.

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