Each October, like clockwork, a dear friend of mine reminds me to begin taking vitamin D supplements– just in time for the perils of daylight savings time. His reasoning? Its prophylactic effects against seasonal depression. In his words: “[it is] the most important thing you can do for your mental health.” For many years, I haphazardly followed his advice, both out of the appreciation I had for him to think about my wellbeing in the face of winter’s darkness, but also because I figured, why not? But can regularly taking vitamin D really have such an effect?
A SAD Winter
is a term that many readers may be familiar with. SAD is distinguishable from other forms of depression in that symptoms begin and end at the same time annually and are typically experienced during the winter months. Those who experience SAD often find relief in the spring and summer months; however, this is not the case for all individuals. SAD, at its mildest, can present itself as winter blues, and is referred to as among healthcare providers. Healthcare providers report that about this milder form. However, when we talk about SAD in its full-blown state, these feelings of depression are far more incapacitating. Individuals with full SAD usually find that their daily lives are impacted, experiencing changes in how they feel and think. About 2-3% of Canada’s population experiences this more extreme form.
Causes of Seasonal Depression
Due to the nature of SAD, researchers hypothesize that its onset is specifically linked to differences in the amount of sunlight individuals receive when the seasons change. According to The Centre for Addiction and Mental Health (CAMH), Canada’s largest mental health teaching hospital, there are theories as to why the changes in light may induce SAD. The first is that changes in sunlight exposure may upset one’s biological clock, which is ultimately responsible for sleep-wake patterns. The second is that a lack of light may disturb neurotransmitter activity.
Disrupted sleep is a symptom not only linked with SAD, but also with clinical depression. Individuals who are diagnosed with clinical depression show disrupted , leading experts to believe that the shifting of time due to daylight savings, and a reduction in sunlight may also present similar symptoms among those experiencing SAD. In fact, one study that some people never fully adjust their circadian rhythm to follow daylight saving time, with these individuals continuing to sleep in late and go to bed late. This excess sleep and off-skelter clock may also influence the amount of melatonin produced by individuals with SAD. This can cause unrelenting sleepiness, which also disrupts daily rhythms.
Linked to this is the other prominent theory as to what causes SAD: serotonin imbalance. Sunlight helps to , a hormone that contributes to feelings of happiness. However, with winter’s shorter days and general lack of sunlight, there may be chemical implications for your mental health. One study found that individuals with SAD have . SERT is a protein assisting with serotonin transport. Essentially, higher SERT levels leads to lower serotonin. This is because when serotonin is brain cells, serotonin is then taken back to the presynaptic neuron– a.k.a. the place it originally came from. This process terminates the serotonin molecule’s action. Interestingly, this process is targeted by SSRIs, which allows more serotonin to pass between brain cells.
Where does vitamin D fall into all of this? Since access to sunlight plays an important role in determining our vitamin D levels, it makes sense that we would produce less vitamin D during the winter months. Many individuals who experience SAD have a vitamin D deficiency, which can be alleviated by taking vitamin D supplements. At the same time, however, not all individuals who have vitamin D deficiencies have SAD. Further, research investigating whether vitamin D is responsible for causing SAD remains inconclusive, with studies having conflicting findings.
The most common and scientifically backed treatment for SAD is . For individuals undergoing this therapy, they are instructed to sit in front of a 10,000-lux light box for 30-45 minutes. This light exposure is less than direct sunshine but is the equivalent of being outside on a bright, cloudy day. It is much brighter than a typical indoor light, but not blinding like the sun. Individuals are typically instructed to do this first thing in the morning. This therapy helps balance the and, in turn, aids sleep.
To the bottle of vitamin D3 on my dresser: don’t worry, I won’t abandon you. While it may not be the cure to my winter blues, trying to keep a regular schedule might just be. Developing a routine, and trying to get outside, even on a cold day might just be the difference between a dark winter, and an even darker one!
Eva Kellner is a recent graduate from the Faculty of Arts and Science, with a major in Environment. Her research interests include urban green spaces, urban agriculture, and outdoor community spaces - all as promoters of climate resilience among city-dwellers.
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