Hi folks   Finally, here is instalment number two of my ‘who, why, what, where, when and how’ of Seasonal Affective Disorder – SAD - and Winter Blues.  I’ll warn you – it’s a long one!

In this post I’ll be covering a couple of the accepted theories of why people get SAD and Winter Blues / Winter Depression.  This is my own understanding, based on what I’ve read over the years and a little background reading I’ve done for this post.  It’s taken me quite a while to write, as I keep changing my mind what to put in!  I don’t want to overwhelm you with too much info, but wanted to give you enough too.  As always, do let me know what you think?

Anyhoo… the first thing to say is that nobody seems to really know what causes SAD and Winter Blues!  There’s a lot of theories, but it’s very likely that there’s a complex interplay of factors that will determine whether a particular individual develops SAD or not.

The most commonly held theory is that a lack of exposure to daylight in the late autumn to early spring months affects the brain’s production of the hormone melatonin and the neurotransmitter serotonin.

The body has an internal body clock, known as the circadian rhythm.  It regulates sleep/wake cycles, appetite, digestion, mood and many other functions.

Before we learned to artificially light our homes, people went to bed when it became dark and woke when the sun rose.  They also spent a lot more time outdoors and had more physical jobs.

The brain responds to decreased light by increasing production of the hormone melatonin, which signals to the body that it’s time to sleep.  In the morning, when light reaches the eyes, melatonin levels begin to decrease and the hormone cortisol is released.  This gives us the get-up-and-go that we need to start the day.  In the depths of winter, when many of us need to get up while it’s still dark, the body hasn’t received the correct signals to wake up.  This is why it can be a real wrench to get up and why you may feel shocked out of sleep by a traditional alarm clock – your body simply isn’t ready to be awake!

But the problem isn’t only to do with waking… with very dull days, your levels of melatonin can stay high throughout the day, leading to those feelings of lethargy and sleepiness that you might recognise all-too-well.  Before I was diagnosed with SAD, I would return from college and want to go straight to bed – I couldn’t keep my eyes open!

The neurotransmitter, serotonin, is also thought to have a key role to play in SAD, as it appears to in other types of depression.  Researchers have found that levels of serotonin can vary from day-to-day and across the year, with levels markedly lower in winter.  People with lower levels of serotonin appear to be more likely to experience symptoms of depression, SAD, Winter Blues / Winter Depression and even PMS in women.

Reading about how to increase serotonin in the human brain without drugs (Dr. Simon N. Young, 2007), this theory makes sense to me.  If you’re anything like me, in winter you’ll be less likely to go outside at lunchtime, or whenever (funnily enough, I don’t enjoy sitting in the freezing wind and rain as much as I enjoy reading a book in the sunshine in the summer! ).  Often eating at my desk means I move my bones less, get less natural light and I’m probably eating stodge, too.  I mean - who really fancies a salad in the middle of winter?  Certainly not me!

Haha – yes, yes, I’m aware that I don’t always follow my own advice!

So, if light, exercise and a healthy diet are major natural ways of increasing serotonin production, then it would seem to follow that not doing/having these things may cause you to feel rubbish.  At least, that’s how I’m understanding it!

As always, if you haven’t already, I’d recommend you have a look at the following excellent articles about SAD, which explain a bit more of the why in more medical terms than I have done:
NHS
Mind

If you’re interested in doing a bit more digging around into theory, here’s a few other theories that caught my eye:

People who suffer from SAD may have retinal sensitivity anomalies -
Evidence of a Biological Effect of Light Therapy on the Retina of Patients with Seasonal Affective Disorder - Marie-Pier Lavoie,Raymond W. Lam,Guylain Bouchard,Alexandre Sasseville,Marie-Claude Charron,Anne-Marie Gagné,Philippe Tremblay,Marie-Josée Filteau,Marc Hébert (2009), Biological Psychiatry, Elsevier

People who suffer from SAD have lower levels of cortisol production in winter -
Seasonal differences in the diurnal pattern of cortisol secretion in healthy participants and those with self-assessed seasonal affective disorder - Thorn, Lisa and Evans, Philip D. and Cannon, Anne and Hucklebridge, Frank and Clow, Angela (2011), Psychoneuroendocrinology

I’ve said to my mum and friends several times in the past that I bet there’s a correlation between babies born in spring and summer and high incidence of SAD… I should have put money on that, as it appears to be true!  I can’t find the published article, but this is what was reported in the Daily Mail.

There’s a lot of debate still ongoing, though, as many of the theories don’t give absolute or satisfactory answers.  So for example, suppressing melatonin doesn’t ‘cure’ SAD; anti-depressants don’t work for everybody; not everyone born in spring/summer suffers with SAD.  It really does seem that individual differences can play a big part.  So you may be more at risk of developing SAD if you or your family have a history of depression, if you’ve been under chronic stress, or sudden stress, such as bereavement.  If you suffer from depression that isn’t seasonal, it can feel worse in the winter.

Having said that, there does seem to be strong evidence to support the theories surrounding melatonin and serotonin having a key role to play.  Correspondingly, there’s also strong evidence to support light therapy.  If you want to do some more reading still, have a look at Lumie’s page of research abstracts.

I hope that this will have been a helpful post for you.  Do you think there’s anything I need to add?  What other theories have you read?

Speak soon

- Neens -

Image credit
Alarm clock: http://www.sxc.hu/browse.phtml?f=download&id=1146532