What causes SAD?

A little bit of history first

Think back to a time when we lived a life that was more in tune with the seasons, this can be as little as a few hundred years ago.  More often than not people in those times rose with the sunrise and rested when the sun went down.  Our lives revolved around the creation of food and a safe place to live. In the spring and autumn there was lots to do; hunting, tending the fields and gathering wild food but in the winter there was much less work so we rested more.

Think now about what there was to eat; in late spring, summer and early autumn there were fresh fruits and vegetables but in the winter diet was restricted to what could be stored and made into warming food to get us through the cold days.  This means that our winter diet was much higher in carbohydrates and protein and lower in fresh fruit and veg.

The cycles of our lives and activity were very much in line with the seasons; we worked hard in the good weather and gathered together around the fire in the winter and our bodies have evolved to suit this lifestyle.

Unfortunately we don’t live in that world any more.  Society insists that we live at the same pace of life all year round.  Our work lives mean that we must get up at the same time in the morning no matter when the sun comes up.  Society implies we should socialise, stay slim and force ourselves to exercise when during the winter, deep in our souls, the more natural part of us is screaming to stop, rest, conserve energy and survive the colder weather.  Whereas we would gain weight in the winter and work it off in the spring we now overeat through the winter and expect to be slim as soon as the wooly jumpers come off, complaining that we need to diet and exercise to achieve what we want.

So what does all this mean?  How can we transfer this understanding to what we experience now?

It is not known exactly what causes SAD on a physical level but there are a number of theories, the main two are:

  • Our bodies have a process known as the circadian rhythm and this is affected by the day length, as days shorten our rhythm changes.

  • Reduced exposure to sunlight leads to reduction in the production of Vitamin D.

I personally believe that for some their SAD is caused by one or the other of the above, but for a few people it is both.  When looking to treat SAD all I can suggest is you read on, listen to your body and see what works for you.

Circadian Rhythms

From my research I have found that the circadian rhythm is responsible for the creation of a number of hormones that control the wake/sleep cycle.  This is a natural process that the brain goes through and is connected to exposure to light levels, particularly sunrise and sunset times.  As the sun rises and we are exposed to an increase in light levels the production of these hormones tails off and we wake naturally.  As the sun sets the production resumes and we begin to feel sleepy.

This is fine when our lives are in tune with the seasons like those of our ancestors, but when we expect to be able to get up at the same time every day to go to work and then have the same bed time at night we are going against these natural flows.  In the summer this is not a problem as we enjoy waking early and making the most of the long days.  However, when winter comes we find that our brains, still flooded with these sleep hormones, refuse to work in the same way.  When this happens we can experience fatigue, brain fog and irritability because our body is telling us we should be asleep.

I personally also believe that when we try to ignore our body’s call for sleep we can also experience anxiety and depression.

All is not lost though; light therapy can help with these symptoms

Vitamin D Deficiency

Our bodies create Vitamin D through the skin being exposed to bright sunlight, no other process in the body creates this vitamin and we cannot obtain enough from our food with a normal balanced diet.  In one resource I read it suggested that it is necessary to receive 20 minutes of full summer sun on bare arms and legs every day to be able to create enough Vitamin D naturally.  Another suggests that anyone who lives above 40º latitude will not receive strong enough sunlight through the winter to produce enough vitamin D.

 A link has been found between Vitamin D, brain function and depression.  Considering the amount of sun we are able to get in the winter it is clear to see that it could be connected to the depression aspect of SAD as the amount of sunlight we are exposed to is reduced as we pass through the year.

I personally believe that Vitamin D deficiency is a chronic problem now.  With growing fears of skin cancer leading to increased use of sunblock combined with more and more people working indoors we are simply not getting enough sunlight at any time.  I believe much of the clinical depression we witness could be connected to this.  In the summer we receive just enough sunlight to keep us ticking over, when winter comes and we get even less our levels crash and we begin to suffer.

 On my page Vitamins and Supplements I talk about what I suggest can be done about this.

 There is one other factor that I think is important to mention….


Although I have outlined what I believe are the 2 main causes of SAD I also think that attitude to winter can have a powerful effect.  How we view the changes of the seasons and how that affects our lives makes a big difference.  If we refuse to accept that winter is a time to slow down and rest we will be fighting against our natural instinct.  If we fear the effects of winter we can set ourselves up to suffer before winter has even started.

Take a look at The Body, The Mind and The Soul pages for information on how you can build up a toolkit to help you get through the winter.