Seasonal affective disorder

Feeling Lighter and Brighter in The Darker Months

A very warm welcome from a grey and foggy Zurich.

It’s getting COLD here. Only days ago, I could see the cows grazing from my upstairs office window. Today I can hear the familiar sound of their bells in the distance, but I can’t see more than 10 feet through the fog.

It seems that autumn is in transition – from the gorgeous season of golden light to the long winter in waiting.  

This can be a tough time of year for many of us as the drear outside seems to make its way in. We may feel a little down or downright exhausted – wondering what we can do to rescue our mood and revive a little motivation.  

The good news is we don’t have to take these feelings lying down.  Nature (as is often the case) points us towards the answers.

By realigning our routines with the natural rhythms of daylight and darkness, we can gently coax our bodies into balance and guide our good feelings back on track.

Shedding light on the changing seasons

For those of us living in the northern latitudes, the return of the chilly days each autumn signals the slow and steady loss of light each day as we inch closer to winter.

Here in Switzerland, we will see a mere eight hours of sunlight each day by the time we reach the winter solstice. The further we live from the equator, the more pronounced these effects can be.

These seasonal swings in daylight have profound impacts on our physiology.

Here’s why.

Each of us has an innate biological rhythm, known as our circadian rhythm, that determines when specific biochemical, physiological, and behavioural processes are designed to occur.

This ancient feature of our biology, shared with nearly every lifeform on the planet, evolved to help us anticipate changes in our environment (such as food availability and temperature) and to help us manage our energy more efficiently by cycling us through ordered phases of activity and rest. What’s key is that these phases of activity and rest evolved to align with the cycles of daylight and darkness. We are inextricably linked to the movements of the earth around the sun.

While our waking and sleeping rhythms are readily apparent, it might be a surprise to learn that nearly all of our critical biological functions follow predictable rhythms of activity and rest based on the cycles of daylight and darkness.

When we live in harmony with these natural rhythms, we feel better, and our health has the potential to thrive.

When we live out of sync with these rhythms, our health suffers and we develop unwanted symptoms as our bodies become more inflammatory, our hormones become imbalanced, and the systems that regulate our energy balance, mood, and sleep become increasingly distressed.

Over time, we may become more vulnerable to serious health issues including obesity, metabolic dysfunction, depression, and even some forms of cancer.

One of the keys to keeping our circadian rhythms running smoothly, it turns out, is getting the right kind of light at the right time of day.

Why is light so important?

Our circadian rhythms are regulated by networks of internal clocks that keeps our rhythms running on a roughly 24-hour schedule. But to keep our rhythms in sync with our environment, our bodies rely on external cues. And the strongest cue for humans is light.

Each morning when the sun rises, sensors in our eyes measure the light and transmit this information to our suprachiasmatic nucleus (SCN), a cluster of neurons located in our brain’s hypothalamus. The SCN serves as our body’s master clock and sends time signals to clock genes located throughout our entire body. Morning sunlight resets the master clock each day to solar time and helps to keep our internal clock networks synchronized.

The SCN also regulates the release of hormones, such as cortisol and melatonin, which signal our cells, tissues, and organs to ready themselves to support “active” or “rest” phase physiology. In humans, active phase physiology corresponds with daylight, and rest phase physiology corresponds with darkness. 

Melatonin communicates to the body that it’s dark and is only synthesized in near total darkness. Melatonin is suppressed in the presence of light, even in small amounts.

The amount of melatonin our bodies produce is directly related to the duration of light to which we are exposed. Melatonin production is in fact higher in the darker autumn and winter months. This is one reason we feel more tired. But melatonin production is also influenced by our 24/7 access to artificial light, which can make things a little confusing for our bodies.

While we typically associate melatonin with sleep, in fact all of our cellular functions are reacting to this signal of darkness and rest. When our melatonin signalling becomes disrupted (for example, through light exposure at the wrong time), our rest physiology becomes disrupted as well. This means that not only do we experience sleep disturbances that leave us feeling less alert, but we may lose the full benefit of our body’s regenerative functions as well.  Melatonin is in fact one of our body’s most important antioxidants and plays a critical role in protecting us from oxidative stress and neurodegeneration.

It’s therefore critical to our health and wellbeing that we experience full darkness at night.

Light and our modern lifestyle

Our circadian rhythms naturally adjust to the changes in light each day. Even small changes in our circadian rhythms have been found to trigger mood disturbances, so it’s not surprising that mood changes are common this time of year.

But what’s even more problematic, in terms of how we feel, is that our lifestyle becomes increasingly out of sync with cycles of daylight and darkness with each passing day. The more stress we already face, the more these natural stressors may affect us.

While just 200 years ago we would have instinctively adjusted our routines to the changes in natural light, we can now be productive at any hour of the day thanks to the availability of artificial light. Our modern work and school schedules tend to remain the same throughout the year, no matter that the natural sunrise and sunset may shift by several hours over the course of a season.

So, while our bodies are carrying out “rest phase” programming, we may be starting on our first cup of coffee, eating breakfast, and heading off to work or school in the dark. This disconnect between the signals of darkness and our metabolic activities can desynchronize our internal clock network with negative ramifications for our health.

If we have an office job, we then go on to spend most of our time indoors. Statistics indicate that people in industrialised societies now spend almost 90% of their time indoors with minimal exposure to natural light as compared with our nomadic ancestors who spent most of their time outdoors. And not only do we miss out on bright light exposure during the day, but we also return to brightly lit homes in the evenings when our bodies expect it to be dark.

While the adoption of LED lighting in recent years promotes better energy efficiency, studies have found that homes with LED lighting are 90% brighter on average than homes with traditional incandescent lighting.

If we are not intentional with how we manage our light exposure, we may wind up with chronically dysregulated circadian rhythms.

We are furthermore exposed to excessive blue light at night through use of our smartphones, computers, eReaders, and TV screens. This is problematic because the short blue wavelengths emitted by our devices mimic the spectral composition of natural daylight, to which we are particularly sensitive.

This means that when we are tapping away on our laptop in bed or watching TV as we fall asleep, we are inadvertently sending our circadian clocks the signal that it’s daytime. And we are suppressing the production of melatonin and potentially dampening the potential of one of our body’s most regenerative resources. 

Overall, many of us are exposed to too little bright daylight during the day and too much bright light at night. This is disrupting our circadian rhythms and confusing our body’s complex timekeeping system.

And, when our bodies must additionally cope with the natural biological stress of the changing light each season, we may push our bodies even further out of balance.

What can we do about it?

The good news is that by making some small adjustments to our daily routines, we can gently coax our circadian rhythms into balance.

Here are some tips to help you get the right amount of light at the right time of day.


Going out for a daily walk before breakfast is a wonderful way to brighten your morning while enjoying some healthy movement. In addition to resetting your master clock, morning sunlight supports your body’s transition from melatonin to cortisol production, which helps you start the day feeling focused. Bright daytime light exposure also boosts serotonin production, which will help give your mood a boost.

If you need some extra motivation to get your new walking habit going, try downloading a new audiobook that you’re excited to listen to. While tuning into the sounds of nature is a great way to encourage mindfulness, a little entertainment can provide a needed boost in the beginning.

And if you can’t get out for a walk? Here are some other ideas to increase your bright light exposure:

  • Enjoy your morning coffee or tea in the brightest room in your house
  • Seat yourself close to a brightly lit window while you work
  • Take a scheduled phone call or meeting outside
  • Take up a new hobby that gets you outdoors (photography anyone?)

Aim for a minimum of 30 – 60 minutes of bright light exposure daily.


If spending more time outdoors is not workable right now, consider bright light therapy. This is a scientifically validated treatment for individuals who suffer from seasonal affective disorder, and it’s been found to improve mood-related symptoms in just a few days.

Bright light therapy, as the name suggests, involves use of a small lamp or light box that shines a safe amount of bright light indirectly into your eyes.

Most bright light therapy lamps deliver about 7,000 to 10,000 lux at a distance of about 20 – 35cm from your eyes. As a point of reference, light intensities in standard offices reach only 500 lux as compared with the 25,000 lux we receive in full daylight.

This therapy is most successful when delivered daily for at least 30 to 60 minutes, ideally in the early morning hours. It’s not necessary to look directly into the light source but rather to let it shine indirectly, glancing at it periodically. Be sure to read the manufacturer’s instructions for your device.

Be warned that these lights are VERY bright, and they take some getting used to. Start slowly to avoid headaches or eye strain. While these devices can be purchased without a prescription, it’s wise to consult a sleep specialist if you have significant challenges with your sleeping and waking schedule. A specialist can advise the best time of day and length of time to use your device.


Make it a habit to turn down all the overhead lights at least 2 to 3 hours before bedtime. You can set a friendly alarm in your smartphone to remind you. Minimise your exposure to blue light emitting devices including your phone, eReader, and television screen. If you cannot avoid blue light exposure, consider getting yourself a pair of blue light blocking glasses.

Many smartphones now have a “warm” setting, which aims to filter out the blue wavelengths. While early studies have found that this adjustment does reduce activation of melanopsin (sensing pigments that register daylight) an even more effective adjustment might be to dim the smartphone down to the minimum level of brightness.

If you’re exposed to any outdoor lights such as streetlights, consider black out curtains. And be mindful of those ubiquitous “on” lights on minor electrical devices lurking throughout your bedroom. Even small flashes of light (in the milliseconds) have been found to suppress melatonin production, resulting in sleep delays and shallower sleep.


Try to maintain a consistent sleep schedule, even on the weekends. A consistent routine will help train your circadian rhythm.

If you have difficulty transitioning to sleep at night, consider instituting an evening winddown routine two hours before bedtime.

Begin with turning down all the lights and experiment with relaxing activities that support you to feel sleepy.

  • guided relaxation
  • a warm bath or shower
  • a cup of calming herbal tea
  • aromatherapy
  • writing in a journal to clear away the day…  

The important thing is to have a transition period between the active phase of your day (this includes watching evening Netflix!) and your nighttime sleep phase.

Try different things and make it a point to notice what truly helps you the most. You are more likely to stick with your new routine once you’ve experienced the benefits first hand.


And lastly, why not take a cue from nature? Remember that darkness cues your body that it’s time for rest. Try to embrace this time of year as a period of rest and hygge.

Stock up on natural scented candles, warm blankets, good books, and cosy moments with friends and loved ones.

Commit to 7 – 9 non-negotiable hours of sleep at night. Sleep an extra hour if your body asks for it and give in to a short afternoon nap if you need it.

Use your body’s invitation for more rest as an opportunity to experiment with new types of relaxation. 

Choose more relaxing forms of movement in the evenings to help you wind down. Rigorous evening workouts boost cortisol and delay melatonin production at precisely the time your circadian rhythm is working to support relaxation and sleep.

Time your energy-boosting workouts for the morning hours when they will help boost cortisol production and support increased focus.

If you enjoy cooking, it’s a great time of year to experiment with new recipes. Cooking with vibrant seasonal vegetables and spices is a great way to treat your senses to some extra colour in a season that can otherwise be overwrought with grey.

Try my vegan sweet potato & lentil curry below.

And if stress is getting in the way of slowing down right now, be sure to read my post on Finding Balance in Seasons of Stress.

I hope you found these tips helpful.

References and Bibliography

Allada, R. and Bass, J. (2021) Circadian Mechanisms in Medicine, The New England Journal of Medicine, 384: 550-61

Blume, C., Garbazza C. and Spitschan, M. (2019) Effects of light on human circadian rhythms, sleep and mood, Somnologie (Berl), 23(3): 147–156

Cain, S., McGlashan, E., Vidafar, P., Mustafovska, J., Curran, S., Wang, X., Mohamed, A., Kalavally, V., and Phillips, A. (2020) Evening home lighting adversely impacts the circadian system and sleep, Nature, Scientific Reports, 10, (19110)

Cipolla-Neto, J., Amaral, F., Afeche, S., Tan, D. and Reiter, R. (2014) Melatonin, energy metabolism, and obesity: a review, Journal of Pineal Research, 56:371-381

Daut, R. and Fonken, L. (2019) Circadian regulation of depression: A role for serotonin, Frontiers in Neuroendocrinology, 54(2019): 100746

Potter G., Skene, D., Arendt, J., Cade, J., Grant, P., and Hardie, L. (2016) Circadian Rhythm and Sleep Disruption: Causes, Metabolic Consequences, and Countermeasures, Endocrine Review, 37(6): 584-608

Tam, S., Brown, L., Wilson, T., Tir, S., Fisk, A., Pothecary, C., van der Vinne, V., Foster, R., Vyazovskiy, V., Bannerman, D., Harrington, M., and Peirson, S. (2021) Dim light in the evening causes coordinated realignment of circadian rhythms, sleep, and short-term memory, PNAS, 118(39):1-12

Xie, Y., Tang, Q., Chen, G., Xie, M., Yu, S., Zhao, J., and Chen, L. (2019) New Insights Into the Circadian Rhythm and Its Related Diseases, Frontiers in Physiology, 10(682): 1-19

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