Seasonal Affective Disorder is a type of depression that comes and goes in a seasonal pattern.
SAD can, in some cases, cause depression in the spring or early summer. However, it is more common during autumn and winter, hence why it’s often referred to as the ‘winter blues’ [1]. At other times of year, sufferers tend to see their symptoms disappear [2].
Reduced exposure to sunlight can affect a part of the brain called the hypothalamus, which is responsible for controlling your hormone production. As a result, sufferers of SAD may produce more of the sleep-inducing hormone melatonin and less of the feel-good hormone serotonin [3].
Interestingly, research shows that younger people between the ages of 18 and 30 are more likely to experience SAD [4]. It’s not yet clear why, but one reason could be that younger people are now more vulnerable to stress, anxiety and depression [5].
Women are also more susceptible to the winter blues, being four times more likely to report SAD than men [6]. And with SAD’s links to low production of serotonin and reduced exposure to sunlight, it’s no surprise that those living farthest from the equator in northern latitudes are affected the most [7].
But if we want to understand how to beat SAD, we also need to know its triggers.
What causes Seasonal Affective Disorder?
Most of us know all too well how difficult the winter months can be.
You wake up and go to work in pitch black, only to spend all day in an office and return home again in darkness! It’s no surprise, then, that many of us feel the bite of this seasonal transition.
SAD is linked to reduced exposure to sunlight associated as the days become shorter and colder. Research shows that while only 1% of people experience the winter blues in Florida, SAD affects 9% of people living in Alaska where there is less daylight in the winter [8]. And this can have severe effects on our physical and mental well-being.
It has been shown that people with SAD have more of a protein that assists with serotonin transport in the winter months than in the summer. High levels of this protein lead to lower serotonin activity, thus causing depression. In the summer, when light levels are higher, levels of this protein are naturally lower [9].
Melatonin, on the other hand, is a hormone that is released in response to darkness and causes sleepiness. As winter days become darker, melatonin production increases and, in response, those with SAD become sleepy and lethargic [10].
Are you at risk of SAD?
The body uses sunlight to time various important functions in the body, otherwise known as circadian rhythm. This internal clock regulates cycles of alertness and sleepiness, and lower levels of light may disrupt this natural rhythm [11]. For this reason, nurses and other professionals who do shift work may be at more risk [12].
Not getting your rays in can also lead to an overproduction of melatonin, making you feel more lethargic than normal, and an underproduction of serotonin which affects appetite, mood, and sleep [13].
We also know that a lack of exposure to sunlight can reduce levels of vitamin D in the body, which increases the risk of depression [14]. And it is this crucial link with vitamin D that leaves some people at higher risk of SAD than others.
Research shows that people who have darker skin tones need more vitamin D than those with lighter skin tones [15]. In the autumn and winter, supplementing with vitamin D, therefore, becomes crucial. But that’s not the only reason.
Magnesium deficiency is incredibly common in western populations. Yet magnesium is critical for allowing the body to convert vitamin D from its inactive to its active form [16]. Therefore, for most people, supplementing with magnesium as well as vitamin D is important to prevent the seasonal energy dip.
And it’s not just your mood that can take a hit during the winter months; SAD may cause a range of other symptoms that are often confused for other conditions.
What are the symptoms of Seasonal Affective Disorder?
How do you know if you are suffering from SAD? Some of the main symptoms of SAD include:
- Persistent low mood
- Loss of pleasure or interest in normal everyday tasks
- Irritability
- Feelings of despair, guilt, and worthlessness
- Lethargic and sleepy in the day
- Sleeping longer than normal
- Finding it hard to get up in the morning
- Difficulty concentrating
- Reduced sex drive
Unfortunately for our waistlines, SAD has also been shown to increase cravings for carbohydrate-heavy and sugar-laden foods[17]. Research shows that eating a high carbohydrate meal increases brain levels of serotonin, which may explain why we experience these cravings more often in the winter months[18].
Pair this drive for carb-heavy foods with increased lethargy, and we have the perfect storm for reduced gym time and more weight gain as the nights get darker. But it’s not all doom and gloom. There is plenty of evidence to show that SAD can be treated successfully using a variety of methods.
How is Seasonal Affective Disorder treated?
When it comes to SAD, physicians all seem to be shouting the same message: “Let there be light!”.
Light treatment is the first treatment of choice for SAD [19]. This involves sitting by a special lamp called a light box, usually for around 30 minutes to an hour each morning.
The light produced by the box is designed to simulate sunlight and may improve SAD by reducing the production of melatonin and increasing the production of serotonin [20].
Alongside light therapy, exercise and exposure to natural light is recommended. This is because the average light level in most offices is around 2-3000 lux, but we need around 10,000 lux for our internal body clock (circadian rhythm) to function optimally [21].
The great news is that a SAD box provides these vital 10,000 lux.
If a SAD lamp isn’t for you, direct daylight before 12 noon is an alternative, however, you may need to get outside for up to 30-40 minutes on overcast days [22]. But that’s not the only way to beat the SAD this winter.
Read our article for 5 Tips to Take the SAD Out of Winter
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References
[1] Melrose S. (2015). Seasonal Affective Disorder: An Overview of Assessment and Treatment Approaches. Depression Research and Treatment, 2015, pg. 178564.
[2] Galima, S. V., Vogel, S. R., & Kowalski, A. W. (2020). Seasonal Affective Disorder: Common Questions and Answers. American Family Physician, 102 (11), pp. 668-672.
[3] Shahid, Z. et al. (2022). Physiology, Hypothalamus. In StatPearls. StatPearls Publishing.
[4] Melrose S. (2015). Seasonal Affective Disorder: An Overview of Assessment and Treatment Approaches. Depression Research and Treatment, 2015, pg. 178564.
[5] Varma, P, et al. (2021). Younger people are more vulnerable to stress, anxiety and depression during COVID-19 pandemic: A global cross-sectional survey. Progress In Neuro-Psychopharmacology & Biological Psychiatry, 109, pg. 110236.
[6] Melrose S. (2015). Seasonal Affective Disorder: An Overview of Assessment and Treatment Approaches. Depression Research and Treatment, 2015, pg. 178564.
[7] Melrose S. (2015). Seasonal Affective Disorder: An Overview of Assessment and Treatment Approaches. Depression Research and Treatment, 2015, pg. 178564.
[8] Melrose S. (2015). Seasonal Affective Disorder: An Overview of Assessment and Treatment Approaches. Depression Research and Treatment, 2015, pg. 178564.
[9] Melrose S. (2015). Seasonal Affective Disorder: An Overview of Assessment and Treatment Approaches. Depression Research and Treatment, 2015, pg. 178564.
[10] Melrose S. (2015). Seasonal Affective Disorder: An Overview of Assessment and Treatment Approaches. Depression Research and Treatment, 2015, pg. 178564.
[11] Reddy, S., Reddy, V., & Sharma, S. (2022). Physiology, circadian rhythm. In StatPearls [Internet]. StatPearls Publishing.
[12] Melrose S. (2015). Seasonal Affective Disorder: An Overview of Assessment and Treatment Approaches. Depression Research and Treatment, 2015, pg. 178564.
[13] Melrose S. (2015). Seasonal Affective Disorder: An Overview of Assessment and Treatment Approaches. Depression Research and Treatment, 2015, pg. 178564.
[14] Parker, G. B., Brotchie, H., & Graham, R. K. (2017). Vitamin D and depression. Journal of Affective Disorders, 208, pp. 56-61.
[15] Libon, F., Cavalier, E., & Nikkels, A. F. (2013). Skin color is relevant to vitamin D synthesis. Dermatology, 227 (3), pp. 250-254.
[16] Uwitonze, A. M., & Razzaque, M. S. (2018). Role of magnesium in vitamin D activation and function. Journal of Osteopathic Medicine, 118(3), pp. 181-189.
[17] NHS. (2020). Overview – Seasonal Affective Disorder (SAD). https://www.nhs.uk/mental-health/conditions/seasonal-affective-disorder-sad/overview/. [Accessed 12/09/2022].
[18] Wurtman, R. J., & Wurtman, J. J. (1995). Brain serotonin, carbohydrate-craving, obesity and depression. Obesity Research, 3, supplement 4, pp. 477S-480S.
[19] Gordijn, M., ‘t Mannetje, D., & Meesters, Y. (2012). The effects of blue-enriched light treatment compared to standard light treatment in Seasonal Affective Disorder. Journal of Affective Disorders, 136 (1-2), pp. 72-80.
[20] NHS. (2022). Mental Health Conditions: Seasonal Affective Disorder. https://www.nhs.uk/mental-health/conditions/seasonal-affective-disorder-sad/treatment/ [Accessed 12/09/2022].
[21] Blume, C., Garbazza, C., & Spitschan, M. (2019). Effects of light on human circadian rhythms, sleep and mood. Sleep Research and Sleep Medicine, 23(3), pp. 147–156.
[22] Boubekri, M., et al. (2020). The Impact of Optimized Daylight and Views on the Sleep Duration and Cognitive Performance of Office Workers. International journal of environmental research and public health, 17 (9), pg. 3219.
