Do you get the winter blues? You’re not the only one. Each year, roughly 5 percent of the country deals with seasonal affective disorder, or SAD. This form of depression develops in the winter and goes away come spring.1
To treat SAD, it’s good to know how it develops. Here are the three major causes of seasonal affective disorder.
1. Low Vitamin D
Seasonal affective disorder is often caused by low vitamin D levels. But unlike most nutrients, deficiency has nothing to do with diet. It’s actually related to sunlight.
Sun exposure helps your skin make vitamin D. Specifically, ultraviolet-B radiation is needed to convert it from 7-dehydrocholesterol.4 However, this vitamin isn’t naturally available in most foods, so you need to get enough sun. Vitamin D is also needed for normal brain function. It’s linked to higher levels of dopamine and serotonin, two neurotransmitters that control your mood.5 6
During the winter, there is less sunlight. The days are shorter and the nights are longer. Plus, the cold might make you want to stay indoors! You’ll be less likely to soak up enough sun to make vitamin D.
It explains why SAD is more common in places that don’t get a lot of sunlight.7 To boost your intake, consider vitamin D supplements. You can also get some vitamin D from salmon, tuna, beef liver, fortified orange juice, milk, and cereal.8
2. Low Estradiol Levels
The primary sex hormone in females is estradiol. If levels are low, depressive symptoms can crop up.9
Interestingly enough, a large Norwegian study found that estradiol levels change with the seasons. It reaches its peak in June. Come October, it reaches an all-time low. The changes were small, yet noteworthy.10
These findings might explain why SAD is four times more likely to affect women than men. The risk also increases if you already struggle with bipolar disorder, depression, or have a family history of depression.11
3. Circadian Rhythm Disruption
Winter’s extra dose of darkness can also lead to SAD. At night, your brain naturally releases melatonin to promote drowsiness. This is part of your normal circadian rhythm or body clock.
The long nights can disrupt this process. Melatonin production increases, but in some people, it might go too far. The result is a delayed circadian rhythm and yawning – lots of it.12
If you already have depression or low vitamin D levels, this disturbance might boost your SAD risk. You also might be prone to melatonin-induced disruptions if you work at night or travel often.
|↑1, ↑3||Kurlansik, Stuart L., and Annamarie D. Ibay. “Seasonal affective disorder.” Indian Jour. of Clinical Practice 24 (2013).|
|↑2, ↑6, ↑7, ↑11||Seasonal Affective Disorder. National Institute of Mental Health.|
|↑4||Binkley, Neil, Rekha Ramamurthy, and Diane Krueger. “Low vitamin D status: definition, prevalence, consequences, and correction.” Endocrinology and metabolism clinics of North America 39, no. 2 (2010): 287-301.|
|↑5||Eserian, Jaqueline Kalleian. “Vitamin D as an effective treatment approach for drug abuse and addiction.” Journal of Medical Hypotheses and Ideas 7, no. 2 (2013): 35-39.|
|↑8||Vitamin D. National Institutes of Health.|
|↑9||Frokjaer, Vibe Gedsoe, Anja Pinborg, Klaus Kähler Holst, Agnete Overgaard, Susanne Henningsson, Maria Heede, Elisabeth Clare Larsen et al. “Role of serotonin transporter changes in depressive responses to sex-steroid hormone manipulation: a positron emission tomography study.” Biological psychiatry 78, no. 8 (2015): 534-543.|
|↑10||Bjørnerem, Åshild, Bjørn Straume, Pål Øian, and Gro KR Berntsen. “Seasonal variation of estradiol, follicle stimulating hormone, and noteworthy androsterone sulfate in women and men.” The Journal of Clinical Endocrinology & Metabolism 91, no. 10 (2006): 3798-3802.|
|↑12||Emens, Jonathan S., and Helen J. Burgess. “Effect of light and melatonin and other melatonin receptor agonists on human circadian physiology.” Sleep medicine clinics 10, no. 4 (2015): 435-453.|