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Updated: Dec 30, 2020


You may have grown up hearing the term “winter blues” and shrugged it off as just an old adage, nothing too serious...

Or maybe, if you are anything like me, this time of year you start longing for blue skies and palm trees…

You know the 1966 hit song “California Dreamin’ ” by the Mamas and The Papas? “All the leaves are brown and the sky is grey...” were quite intuitive lyrics for that era. Writers John & Michelle Phillips were certainly ahead of their time when they pointed out definitive ways that dark and cold winter months tend to affect our moods deeply.

In 1984, the term SAD (Seasonal Affective Disorder) was coined[1], and classified, as a legitimate diagnosis affecting a significant portion of the American population. At that time this diagnosis was pretty controversial and not a lot was known about the cause, potential treatment and the detrimental impact of brushing off the symptoms as “no big deal”.

It wasn’t until 2013 that the authors of the DSM-5”[2] had enough data to support the diagnosis of SAD as a legitimate form of Major Depressive Disorder that occurs at specific times of the year. It is no longer considered a form of “severe winter blues” for the “highly sensitive person” and it is rare to find a clinician that will dispute its legitimacy (although there are still a lot of unconfirmed details about its causality).

Needless to say, SAD is not something to just shrug off.

At the best of times it can be overwhelming and can interfere with daily functioning, but this year especially, the pile-up of other factors (extended social isolation, medical fears surrounding COVID-19, civil and political unrest to name just a few) can amplify the effects of SAD and can potentially increase risk of more severe symptoms.

I’m not saying this to be alarmist, only to make sure that our community is proactive in education and prevention efforts. It is important to be knowledgeable about what makes us more susceptible to SAD, what the symptoms and potential treatments are as well as when and how to seek help. It can also help you understand why your best friend or loved one is a bit more withdrawn and unresponsive lately.


The jury is still out on that... But there is a lot more research than ever before pointing to any one of, or a combination of reasons.

It’s a general rule of thumb that whenever the body experiences abrupt changes of any kind (physical, emotional, chemical etc.), there is more of a likelihood that the system will get thrown off kilter, potentially causing challenges to the nervous system, body chemistry, physical or emotional health.

For many people, extreme changes might not be such a big deal, after all, our bodies are naturally built to self-regulate. But for some individuals, there are genetic or developmental factors that make bouncing back a bit more difficult.[3]

If the body can’t find equilibrium on its own, interventions might be required to re-set or support the body’s journey back to balance (sometimes it helps to merely take time and interest in developing a sense of attunement to the body’s new or changing needs. Sometimes it’s not enough though. Hopefully you will be able to tell the difference with enough practice.)

While there is still a lot more research to be done, some evidence and promising studies point to a variety of causes that all seem to circle around circadian rhythm changes and neurotransmitter dysfunctions that all seem to be related somehow to melatonin, serotonin and vitamin D. The links between all of them have not been confirmed due to lack of sufficient data, but they do seem logical (to me, at least).

So, let’s look at what we do know so far and hopefully you can draw your own educated conclusions based on available scientific evidence;


Have you ever heard of a biological clock ticking?

Well, it’s an actual scientific thing. Circadian rhythms are essentially our biological clocks, that when thrown off, can cause physical, mental, and behavioral changes. It is a natural process that affects pretty much all living things.

I’ll try to explain how they work in a nutshell, but if you are interested in learning more about the science of chronobiology you can visit the National Institute of General Medical Sciences (also PSA, I’m not a scientist or a doctor so this is my simplified understanding of what happens and I hope I’m not messing it up [consider this my disclaimer]. It's obviously way more complicated in real life and involves many other factors than this).


Inside almost every tissue and organ there are groups of protein molecules that are in charge of regulating the body’s natural rhythm (AKA biological clocks).

Those bundles of protein molecules are regulated by the suprachiasmatic nucleus, or SCN which is a tiny region of the brain’s hypothalamus that sits directly above the optic chiasm. It is the part of the brain that is in charge of keeping all the biological clocks in the body in sync with each other. It is made up of tens of thousands of neurons (approx. 20,000) that get their orders from the “outside” via input from the eyes’ optic nerves (so let’s call the eyes the “clock informers” and the SCN the “clock regulator” or the “clock boss”).

Each of our senses in general are responsible for taking in information from the outside world and translating that info quickly and often impulsively (in microseconds) so the messages can be understood and received in the right places in the body. Once the messages get to where they need to go, the receptors or “receivers” grab the messages and take immediate action.

This whole process can impact very important functions in our bodies, such as our sleep patterns, hormones, body temperature and digestion.

The way the circadian rhythms function in your particular body will depend on genetic, hormonal, psychological, physiological, biological and environmental factors (among others). It will also depend on the proper functioning of the “senders”, “translators” and “receivers” of input, so understanding a bit about how neurotransmitters, hormones and body chemistry works will be helpful.

So, let’s look at a few factors that are thought to impact circadian rhythm and healthy body functioning;


The SCN is involved in the production and regulation of a hormone called melatonin that is responsible for sleep regulation (you might know of it as a sleeping pill, but it’s really a manufactured hormone).

So here is what happens in winter; When you wake up in the morning and leave for work while it is still dark out,[4] the SCN gets a signal from the optic nerves that it’s night time, which triggers the production and release of more melatonin. Your body intuitively wants to help you get sleepy when it thinks its bedtime because it wants you to have a more restful sleep. The darkness tells your body to hit the snooze button rather than give it a wakeup call.

I actually made the mistake of taking a melatonin supplement first thing in the morning instead of my allergy pills for a few weeks (PSA to label all your meds and supplements when you travel) and I actually thought there was something severely wrong with me. I could not get out of bed and thought I had mono or something even more serious. That is how powerful melatonin is and your body naturally produces it (unless you train it otherwise).


SERT (serotonin reuptake transporter) is the neuro transporter protein responsible for the release and regulation of serotonin (AKA the happiness hormone) which is a huge part of mood regulation.

Studies show that when the SERT protein is actively transporting serotonin, serotonin is not active - and vice versa. There is now a lot of evidence (that can even be seen on PET scans) that shows SERT levels that are significantly higher and serotonin levels are lower during winter, in individuals affected by SAD. Last I read, researchers don’t yet know exactly why but what they do know is, "Sunlight keeps this setting naturally low, but when the nights grow longer during the autumn, the SERT levels increase, resulting in diminishing active serotonin levels.[5]


Although vitamin D is known as one of the four fat-soluble vitamins (others are A, E & K), it isn’t really a vitamin as previously thought.

We now understand that “Bioactive vitamin D” or “calcitriol” actually refers to a group of fat soluble hormones (including but not limited to vitamin D3 [cholecalciferol] and vitamin D2 [ergocalciferol]) known for their important role in immune function, metabolism, regulation of certain vitamins and minerals, heart health and the healthy formation and maintenance of our bones, teeth and muscles (to name just a few). “Vitamin D” also helps to regulate the amount of calcium and phosphates in the body.[6]

The most important source of D3 is produced by the chemical reaction that happens when the sun (specifically because of its ultra violet rays) hits the skin. When the UV energy is absorbed into the skin by a precursor molecule (7-dehydrocholesterol) it becomes D3 which then must be broken down further (somehow involving protein enzymes first in the liver and then in the kidneys) but this process is beyond my comprehension, so I won’t even attempt it.

What is most incredible about “vitamin D” is that researchers are only just beginning to identify its full power. There is a lot that we don’t know. But here is what we do know (well, the parts that seem to relate to SAD, anyways);

  • It is believed that “vitamin D” plays a significant role in serotonin regulation so it makes sense that vitamin D deficiency is also associated with clinical depression symptoms.

  • Genetic defects might be a contributing factor to “vitamin D” resistance, which, if left untreated, can be a cause for related health concerns.

  • Insufficient vitamin D can cause bones to soften, making us more prone to breaks and can also lead to bone deformities (rickets in children and osteomalacia [bone pain] in adults).

  • Severe kidney or liver damage could interfere with the production of “Bioactive vitamin D”, which is the form we need it to be in for it to do any good in our bodies.

  • Insufficient amounts of sunlight can also interfere with the production of “Bioactive vitamin D”. In cultures that tend to cover up most of their bodies when they are outside (or even those that wear UV blocking sunscreen) might start to notice signs of “vitamin D” deficiency.

  • Thankfully, first world countries fortify many food products with D3 supplements which means it is already in the correct form to be sent to the liver and kidneys for processing once digestion starts.

  • Too much exposure to sunlight cannot not lead to vitamin D toxicity (although it can lead to cancer), however, toxicity can happen by overdosing on vitamin D supplements. Before you consider raising your D supplement dosage, check to make sure you are not actually experiencing an absorption or resistance issue and fix that first.

  • It is highly unlikely that you will be able to get sufficient amounts of vitamin D into your body via food alone[7] during the winter unless you are going outside for 20-30 minutes each day and enough of your skin is exposed so you can take in some rays (you can get UV rays even when it’s cloudy). If you are not getting enough sun, supplements might be required.

In recent years it has become more apparent that receptors for vitamin D are in a wider variety of cells than previously thought. It is still unknown to what extent this power hormone impacts our bodies but we know that it’s functions far exceed what researchers had originally thought. In fact, there have been studies that noticed a link between covid-19 susceptibility and vitamin D deficiency.[8]

* * *

Knowing all of this, it makes so much sense that the decrease in serotonin, increase of melatonin and potential vitamin D hormone insufficiencies can seriously mess up the circadian rhythms in our bodies and compromise our overall health and wellbeing.

There are for sure other factors but I'm trying to keep this as brief as possible (it was already 12 pages long so I broke it in to 3 parts lol)

[1] The Recent History of Seasonal Affective Disorder (SAD) Written by Norman Rosenthal and his colleagues at the National Institute of Mental Health in Bethesda, MD. [2] Diagnostic and Statistical Manual of Mental Disorders put out by the American Psychiatric Association [3] In case you are wondering why your sister or child has a susceptibility and you don’t, it’s because that is how genetics works. Not all of you will inherit the same traits - just like some of you might have green eyes and some brown… so try to be patient and understanding of your loved ones that you cannot understand fully. They are doing the best they can given their circumstances. [4] Different regions of the world will have higher susceptibility at different times of the year. [5] [6] Promising research studies show genetic predisposition to the buildup of calcium phosphate deposits throughout the body linked to the cause of all fibromyalgia symptoms (previously thought to be psychosomatic in nature). Although highly controversial for many years, the transformative treatment protocol has been developed by Endocrinologist, Professor at UCLA and Chemical Engineer, Dr. Paul St. Amand, has had very high success rates. New studies are underway to help support his findings. [7] The amount of fish or eggs you would have to eat to reach your daily requirement would likely give you cholesterol problems and eventually heart problems. Vegetables and fruits only have D2 which does not have the same power as D3. [8]

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