Shining Light on Seasonal Depression

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Natural approaches to overcoming seasonal affective disorder (SAD)

As charming as I found the quad of the University in the summer, the winter semesters at my alma mater were brutal. It was cold. It was dark. It was damp. Many of my classmates looked ashen, tired, and miserable. In those dark Canadian winters I heard the term “seasonal affective disorder” – appropriately abbreviated SAD – thrown around constantly. But when I learned that the university’s student clinic had purchased several “happy lights” and that students could sign up for appointments to sit by these special lamps, I realized that SAD wasn’t something my fellow students had invented to excuse lazy behavior; seasonal depression was, and indeed still is, “a thing.” SAD, or “winter blues,” is a type of depression that flares in the autumn and winter and fully remits in the spring and summer.[1],[2]

Medical training aside, I’m quite convinced that the simplest way to prevent seasonal depression is to move to a tropical island with warm, sandy beaches, perfect blue skies, and gentle breezes that rustle the leaves of nearby palm trees.

…But for those of us living in the rest of the world, there’s hope yet. Here are some simple, scientifically-based strategies to help keep seasonal depression at bay:

Light therapy

Light therapy is perhaps the least invasive and most researched treatment for SAD, and for this reason is considered a fist-line therapy for the condition.[3],[4] Light therapy consists of sitting before a bright light for at least 30 minutes one or more times daily.

The sensitivity of the retina (the back of the eye) to ambient light appears to contribute to SAD. Whether it’s caused by fewer hours of sunlight during the days of winter, genetic influences, or physical factors like eye color (it’s thought that the eyes of people with darker-colored irises don’t absorb as much light),[5] the effect is the same: the less light the retina perceives, the worse the brain functions, with both visual and non-visual brain cells affected.[6] In fact, diminished central nervous system perception of light is thought to cause deficits in cognitive function, mood, and alertness, and to exacerbate the circadian rhythm dysfunction commonly seen in SAD.[7]

Diminished central nervous system perception of light is thought to cause deficits in cognitive function, mood, and alertness, and to exacerbate the circadian rhythm dysfunction commonly seen in SAD.

Several studies have demonstrated the efficacy of light therapy – also called light box therapy – in the treatment of SAD.[8],[9] Light therapy works best with the right combination of light intensity (recorded in lux), duration of treatment, and timing. Higher-intensity lights (10,000 lux) yield benefits in as short as 20 minutes a day, whereas lower-intensity lights (such as 2,500 lux) will require longer sessions to create the same benefits. Because UV light can cause injury to the eyes and increase the risk of skin cancer, it’s best to use a configuration that filters out UV. This is often done by placing a simple plastic light cover with UV-filtering properties in front of the bright light.[10] Specifically, the standard recommendation for light therapy is to use a 10,000-lux light box, positioned 16 to 24 inches from the face, for 20 to 30 minutes a day, every morning, through the duration of winter.[11]

Vitamin D

Vitamin D receptors (VDR) have been identified in at least 36 different tissues of the human body, including numerous regions of the brain.[12],[13] Vitamin D also acts as a hormone, affecting the thyroid and adrenal glands, the pancreas, the ovaries and testes, the kidneys, and the digestive tract.[14],[15]

The majority of our body’s vitamin D is produced when the skin is exposed to UVB radiation from the sun. This means those of us living far from the equator tend to have lower blood levels of the nutrient in the autumn and winter as compared to the sunny summer months.[16],[17] With the dip in vitamin D levels comes a dip in mood; low levels of vitamin D have been linked with depression.[18],[19] This risk is greater in people of color, as the more pigmentation there is in one’s skin, the less efficiently the body photosynthesizes vitamin D.[20],[21]

The majority of our body’s vitamin D is produced when the skin is exposed to UVB radiation from the sun. This means those of us living far from the equator tend to have lower blood levels of the nutrient in the autumn and winter as compared to the sunny summer months.

Although commercial lab companies report the normal range of vitamin D levels (measured by the vitamin D, 25-hydroxy test) to be as low as 20 ng/mL,[22] many physicians and researchers call for a lower limit of 30 ng/mL[23], and still other integrative practitioners – aware that the current reference range is based primarily upon the research regarding bone density and does not take into consideration the importance of vitamin D for immune health, hormone signaling, and its myriad other functions – call for an even higher reference range.[24],[25]

Although many mechanisms for vitamin D’s influence on mood have been proposed, one worth mentioning here is the nutrient’s influence on the synthesis of the neurotransmitters serotonin – which plays an integral role in supporting mood, memory, and learning – and dopamine – which controls motivation, thinking, and concentration.[26]

Unsurprisingly, supplementing with vitamin D3 (the active form of the nutrient) has been shown to help those with SAD feel better and to generally improve psychiatric health.[27],[28]

Methylated B vitamins

Flipping through the pages of a biochemistry textbook is likely to be an overwhelming and tedious activity for the average person. But even a cursory consideration of the diagrams should convey an important message: folate and the B vitamins are all over the place, peppering more diagrams than not. These nutrients are important for numerous reactions in the human body, in particular those pertaining to neurotransmitter production and neurological health.[29],[30]

For this reason, those with folate deficiencies are less likely to respond to antidepressant medications, are more likely to relapse, and have poorer cognitive performance,[31],[32],[33] whereas those with adequate intake of folate have been shown to be less likely to develop depression.[34] Folate supplements come in three forms: folic acid, folinic acid, and L-methylfolate. The first two forms require an enzyme known as methylenetetrahydrofolate reductase (MTHFR) in order to convert them to L-methylfolate, the active form of the nutrient capable of crossing the blood-brain barrier (BBB)[35] and activating the synthesis of the neurotransmitters dopamine, norepinephrine, and serotonin.²⁷ Because many individuals have genetic mutations compromising MTHFR function, supplementing with the L-methylfolate form may be a more reliable way to ensure proper folate status.

Because many individuals have genetic mutations compromising MTHFR function, supplementing with the L-methylfolate form may be a more reliable way to ensure proper folate status.

MTHFR mutations can also affect the proper utilization of vitamin B12. Without proper MTHFR function, the cheaper commercially available forms of B12 (cyanocobalamin and hydroxycobalamin) have limited conversion to methylcobalamin, the active form of the nutrient. For this reason, more and more clinicians are choosing methylcobalamin preparations.[36]

Studies have demonstrated the role of folate and B-vitamins in slowing the progression of cognitive decline and possibly reducing the risk of depression in people above the age of 60,[37] and a study of pregnant adolescent females found that those with higher dietary intake of B12 and folate were less likely to suffer from depression.[38] It has also been shown that those with MTFHR genetic mutations are at increased risk of depression.[39] Research suggests that B12 and folate supplementation are more likely to help when taken on a long-term basis, as opposed to a short course of therapy for acute troubles.[40] Because the main source of vitamin B12 comes from red meat, furthermore, vegetarians and vegans are at high risk of becoming deficient.[41] Maintenance supplementation with methylated folate and methylcobalamin may therefore be a simple way to stave off SAD and depression.

In addition to light therapy and these essential vitamins, numerous botanicals, antioxidants, melatonin, and even gratitude-based journaling may play a role in keeping an upbeat mood through the winter and beyond. Click on the hyperlinks to learn more about these holistic approaches to maintaining a positive outlook!

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