By Vijay Moonilal – Content Coordinator
Summers are a fun time, especially during childhood and especially when you grow up in Canada. I love the snow, but my favourite memories are all from summer. Weekends at Canada’s Wonderland (our country’s largest outdoor amusement park), learning how to skateboard with a mountain of protective gear, going to the park with my grandmother to name a few. Though for journalistic integrity I should mention it very well could have been the fact that both my birthday and the end of school was within a couple days of the start of summer. That trend of positive memories continued into my adolescent years.
My summers began to look different at this point. I no longer spent most of it outdoors, skateboarding was replaced by video games, mainly on my Nintendo DS, but I started to feel more tired in the winter months, lost interest in my hobbies, found school harder, and had trouble sleeping. I distinctly remember being thirteen and thinking how strange it is to struggle with both feeling tired and struggling to sleep. I later learned that these symptoms closely aligned with something called Seasonal Affective Disorder.
An exploration of what Seasonal Affective Disorder is.
Seasonal Affective Disorder (SAD) is a type of depression that typically occurs during certain seasons, most often in the fall and winter months when there is less sunlight. It can affect people of all ages, though it often emerges in late adolescence or early adulthood. An important aspect to keep in mind is that while some shifts in mood are normal, bigger shifts in mood and energy levels are when it starts becoming SAD and going into my teen years I started to feel stronger shifts.
At its core, SAD is linked to disruptions in our biological rhythms. As daylight hours shorten, the lack of sunlight can alter the body’s internal clock, also known as the circadian rhythm. This can affect sleep patterns, appetite, and overall mood. Natural light exposure plays a crucial role in regulating our brain’s production of serotonin, a neurotransmitter that helps regulate mood, sleep, and energy levels.
In individuals with SAD, the decreased daylight during the fall and winter months can lead to lower serotonin levels, contributing to feelings of sadness, fatigue, and hopelessness. In fact, the mechanism for this is very direct, there is a bundle of neurons called the suprachiasmatic nucleus, which is considered the central pacemaker of the circadian rhythm. This bundle is directly connected to light sensing cells in our eyes. Much is still unknown about how all these parts fit in together, but disruptions to the circadian rhythm seem to cause both mental and physical health problems.
In Canada, the long, dark winters make it one of the countries where SAD is particularly prevalent. But, as any Canadian will tell you, there are massive differences across the country, however the northern latitude means fewer hours of daylight in the winter months, and, for many, this contributes to a significant drop in energy and mood. In fact, research suggests that Canada has one of the highest rates of SAD in the world, with some estimates suggesting that up to 3% to 6% of the Canadian population may suffer from this condition. Many individuals living in northern regions like Yukon, Northwest Territories, or parts of Quebec and Ontario experience even higher rates of SAD due to the prolonged periods of darkness and colder weather.
While the disorder is most common during the winter months, it is important to note that some people can experience SAD during the summer months as well, known as “summer-pattern” SAD. My best friend experiences this. However, this is far less common, with the majority of SAD cases linked to the darker winter months like mine. But the logic is similar, your circadian rhythm is disrupted instead in the summer, leading to the effects to your sleep patterns, mood, and eating habits.
What impact does SAD symptoms have? For me I find my three strongest symptoms in the winter months are accompanied by a strong mid day fatigue, around 3pm, a mild depression, and I tend to lose interest in my hobbies. For most of my winters since adolescence, this has been something I’ve planned my life around. In university, I used to take my hardest courses first term, as I found it easier to start the term with my higher energy levels then end it, though I’ve always found winter exams particularly challenging for this reason. I distinctly remember being exhausted, outside in the cold, barely able to get out of bed, waiting for one of my neuroscience exams to start, the kicker? The exam had a question on it about which nucleus controls the circadian rhythm and is linked to Seasonal Affective Disorder. I knew that one.
Role of Sunlight and Vitamin D
What have we learned so far? Mostly, that sunlight plays a significant role in how we feel, especially when it comes to our mood and energy levels. But, when the days get shorter and the sun disappears for hours at a time during winter, it can really mess with how our bodies work.
This leads us to another key factor, Vitamin D. We get most of our Vitamin D from sunlight, which is why during the darker months, many people in northern latitudes end up with lower levels of the vitamin. This is important because Vitamin D is linked to better mood regulation, among other things. Lower vitamin D levels have been linked to poorer mental health. Therefore, there are kind of two things happening, one is Canadians have short winter days that mess up our circadian rhythms, and two, these short days lead to less Vitamin D production.
While it’s hard to get that natural sunlight in the winter unless you’re outside a lot (which, let’s be honest, few of us are when it’s freezing outside), taking Vitamin D supplements has become common. I started taking vitamin D supplements every winter about 5 years ago, so Seasonal Affective Disorder cured right? Not exactly, but a step in the right direction. Time to explore another option.
Light Therapy
Light therapy is exactly what it sounds like, exposing yourself to bright light that mimics natural sunlight. This is clinically considered one of the best ways to fight back against Seasonal Affective Disorder (SAD) because it can help regulate your body’s internal clock. The basic idea is we have these light detectors in our eyes which are getting shorter signals in the winter, right? So let’s just artificially extend them. Using the powers of science we have harnessed over the past centuries to fight back against SAD, amazing right? Except…
Light therapy is just sitting in front of a lamp for a long time. Now I am underselling it. The lamp is super bright, way brighter than regular indoor lighting, so it gives your body the sunlight boosts it’s missing. These light therapy lamps emit 10,000 lux of light, which is about 20 times the intensity of your regular lamps. The key to making light therapy effective is timing. Most people get the best results when they do it first thing in the morning, within an hour or so of waking up. This helps reset your circadian rhythm because when your body gets enough light early in the day, it’s easier to feel energized and get into a routine.
The cool thing about light therapy is that it’s safe, easy to use, and it doesn’t require a prescription. Most people tolerate it well, though some might get minor side effects like headaches or eye strain. But these tend to be short-lived and can be avoided by adjusting how close you sit to the light or how long you use it. A relatively simple answer to a complex problem, a rarity in today’s day and age.
For those of us in northern places like Canada, light therapy can make a notable change. It’s not a cure-all, but it can help lift your mood, boost your energy, and make those long winters feel a little more bearable. Even if you’ve just been feeling low during the darker months, it’s worth giving it a shot.
Vitamin D deficiency and Light Therapy in racialized populations
As an Indian person (and by extension a person of colour), I think it’s also important to touch on some research that shows light therapy may not affect everyone the same way. Research has found that while African American and Caucasian patients with Seasonal Affective Disorder (SAD) showed similar improvements in mood after light therapy, African American participants were less likely to reach full remission (Uzoma et al., 2015).
One explanation lies in biology, higher levels of melanin in darker skin and eyes can reduce how much light reaches the retina, and how much vitamin D is produced, potentially making light therapy less effective. This is actually a very interesting evolutionary story, darker skin protects against high UV levels closer to the equator, regions where we tend to find people with darker skin colours, while further away from the equator, lighter skin evolved to allow for sufficient vitamin D production in areas with less sunlight.
However, there has been little follow up work on the findings of the study that point out the differences in remission rates between African American and Caucasian patients with SAD.
Beyond biology, cultural factors play a role too. In many communities of colour, including my own, mental health isn’t always discussed openly, and seeking treatment for a stigmatized topic is a challenge.
Research on Canadian populations has also shown that people of colour, including South Asian, Black, and Hispanic communities, are more likely to have vitamin D deficiency. That deficiency is linked to fatigue, weaker bones, muscle aches, and even a higher risk of immune problems. One study in Ottawa that compared south Asian students to other ethnicities found that there was a higher rate of vitamin D deficiency in these populations and calls to reinforce the importance of public health actions towards meeting vitamin D intake recommendations among those of high-risk deficiency.
Prevention
The last winter was my best for Seasonal Affective Disorder (SAD) symptoms ever. I took my vitamin D and used my light therapy lamp every day before the sun rose, but the biggest piece of the puzzle was shifting my mindset from reactionary to prevention based. I started preparing for SAD in October, with vitamin D supplements, healthy foods, regular exercise, and keeping a strong sleep schedule.
But that’s where the biomedical model of disease treatment often falls short. The biomedical approach tends to focus on treating symptoms after they’ve already emerged, offering interventions like pills, light therapy, or therapy once the condition has already begun to impact your life. This model, while incredibly effective for managing acute health problems, struggles when it comes to long-term prevention, especially for chronic conditions like SAD.
Take everything we’ve learned about SAD so far. While it’s great that light therapy and vitamin D supplements can help manage the disorder, they are reactive tools we use after the effects of seasonal changes have begun to impact our mental health. The problem with this is that the biomedical model rarely addresses the deeper, root causes of why some individuals are more vulnerable to SAD in the first place.
What’s more, the biomedical model tends to treat each individual symptom in isolation. It doesn’t always account for the complex web of interconnected factors – biological, social, and environmental – that contribute to mental health issues like SAD. For instance, while my experience with SAD is partially tied to sunlight and circadian rhythms, there’s also a cultural aspect at play, my ethnoracial identity, which impacts my treatment.
Prevention, in its true sense, requires a more holistic approach. And interestingly, SAD is a notable example of this, since it is a cyclical disorder that is easy to predict it’s onset. Instead of only addressing the physiological aspects of SAD, we need to consider broader lifestyle changes that can reduce the risk of the disorder in the first place.
In this context, prevention isn’t just about taking Vitamin D pills or starting light therapy earlier. It’s about recognizing how much the change in seasons affects me and fostering a lifestyle that minimizes the risk of these shifts.
To anyone dealing with SAD, I would first recommend doing the amazing treatments available that are well known, light therapy, Vitamin D supplements, and maybe even talk therapy. But I’d also say to take on a more integrated approach. Think about building a life that is more resistant to the negative effects of the seasons changing and try to implement those changes during the months you’re thriving. What exactly helps you may, and probably will, be different than what helped me. But I can say with certainty, that shifting your mindset to prevention based instead of reactionary, will help you get through the chilly winter months.
References
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Dark-skinned immigrants urged to take vitamin D | CBC News. (n.d.). Retrieved October 24, 2025, from https://www.cbc.ca/news/canada/ottawa/dark-skinned-immigrants-urged-to-take-vitamin-d-1.945614
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