Vitamin D and Seasonal Affective Disorder (SAD)

Vitamin D and Seasonal Affective Disorder (SAD)

Seasonal Affective Disorder

In our current fast-growing society, depression and anxiety have become major concerns for public health. One particular disorder that affects many people is seasonal affective disorder (SAD). It is classified as depression related to climate and seasonal weather change, and it typically occurs in autumn and winter with remission in spring or summer.¹ Although the condition is seasonally limited, people may have significant impairment from the associated depressive symptoms.

There are many treatment options for seasonal affective disorder such as:
Light therapy
Cognitive behavior therapy
Antidepressants

According to the American Psychiatric Association, SAD has been linked to biochemical imbalances in the brain that are prompted by shorter daylight hours and less sunlight in the winter, and it is common among people who are living farther from the equator where there are fewer daylight hours in the winter.³ However, one may ask what the human body uses sunlight for and how does this decrease in sunlight results in SAD. Through scientific research, we know that the human body uses sunlight to make vitamin D. There is an accumulating number of studies indicating that vitamin D acts as a neuroactive steroid, which plays a key role in the expression of neurotransmitters, regulation of neurotrophic factors, neuroimmunomodulation, production of antioxidants and neurotrophic factors.² Hence, it is thought that a low vitamin D level is associated with depressive symptoms.

Vitamin D

Vitamin D is a fat-soluble vitamin, and it can either be obtained from diet or synthesized from 7-dehydrocholesterol upon sunlight exposure of the skin. Vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol) are the main precursors of active vitamin D hormones. Vitamin D must be activated in the body for it to function properly. In the human body, vitamin D is used to aid the absorption of calcium and phosphorus in the intestinal tract, so when it is too low, it can result in electrolyte imbalance. When the nature of the body is out of balance, stress, and anxiety are among the noticeable symptoms.

In addition, vitamin D receptors are located in many tissues throughout the body including the brain, specifically in the prefrontal cortex, hippocampus, cingulate gyrus, thalamus, hypothalamus, and substantia nigra.⁴ These regions of the brain are important as they are defined in the pathophysiology of depression, and it has been determined that vitamin D activating enzyme 1-alpha-hydroxylase is widely distributed in many different cell types of many brain regions, especially in neuron in amygdala and glial cells in hypothalamus.⁴ In other words, low vitamin D levels could affect the functions of these regions of the brain in mood regulation.

What can you do?

To reduce the risk of seasonal affective disorder, one could simply get outside of the house more often to catch some sunlight during autumn and winter. However, this can be very difficult, because most people don’t spend a lot of time outside during the colder months and they definitely don’t have a lot of skin exposed. DMinder is an app that takes into account your location, time of day, and skin exposure and can help track sun exposure and the resulting vitamin D production.

Light Therapy

Light therapy is considered the first-line treatment for people who suffer from SAD.⁹ Studies dating back to 1982 have shown how treatment with bright white light can improve symptoms.⁶ You don’t have to sit in front of a light for hours on end. Studies have shown that a bright light intensity of 10,000 lux for 30–45 minutes per session is sufficient to see results and most people see improvements after a few days with standard treatment length being around 1-2 weeks. Blue light therapy is a more recent development in the treatment of SAD. Head-to-head studies of bright white light vs. blue light therapy showed no difference in the improvement between groups (both groups showed similar improvement).⁷ Dawn simulation is another form of light therapy that not only improves SAD symptoms but has positive effects on waking up without shifting the biological clock. Dawn simulation is when there is a gradual increase of artificial light simulating sunrise.⁸ This is less time-consuming for people as the light therapy is received while they are still sleeping.⁹

Supplement

Before you head to the pharmacy, it’s a good idea to check your vitamin D levels at home or ask your PCP to check them for you. We have an at-home vitamin D test available at our store if you’re interested. Since vitamin D is fat soluble, it can be toxic to the human body at high levels. Too much vitamin D can cause loss of skin turgor, dry mucous membranes, changes in mental status, and abdominal tenderness.⁵ Once you know your level, you can work with a provider to determine your optimal level of vitamin D and the dose needed to get you there. Despite the NIH’s recommended dietary allowance, often our patients aren’t getting to goal levels. You can schedule a brief supplement consultation with any of our team to discuss goal levels and get specific recommendations. Find a provider here.

If supplements aren’t your thing, you can also increase your vitamin D level by eating more foods rich in vitamin D. These include certain fish, egg yolks, and mushrooms. Although these foods have vitamin D, often they are still not enough to reach optimal levels, so it is still important to get your levels tested.

If you are someone who is affected by SAD, hopefully, you are able to take what you read and put it to good use! If you are looking for a practitioner to work with to determine your supplement dosage for vitamin D, check out our provider page. A simple brief supplement consult would be a great place to start for this!

Written by James Vo, PharmD Candidate
Edited by Lindsey Dalton, PharmD

References:
1. Munir S, Abbas M. Seasonal Depressive Disorder. Published January 2023. Accessed September 2023. https://pubmed.ncbi.nlm.nih.gov/33760504/
2. Chunmei Geng et al. Vitamin D and Depression: Mechanisms, Determination, and Application. Accessed October 2023. https://apjcn.nhri.org.tw/server/APJCN/28/4/689.pdf
3. Kurlansik S, Ibay A. Seasonal Affective Disorder. Published December 2012. Accessed September 2023. https://pubmed.ncbi.nlm.nih.gov/23198671/
4. Vitamin D Fact Sheet for Health Professionals. National Institution of Health. Updated September 2023. Accessed September 2023. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/#:~:text=Most%20people%20in%20the%20United,in%20women%2C%20and%204.9%20mcg%20(
5. Vitamin D Toxicity. National Institution of Health. Updated May 2023. Accessed October 2023. https://www.ncbi.nlm.nih.gov/books/NBK557876/
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8. DanilenkoKVIvanovaIADawn simulation vs bright light in seasonal affective disorder: treatment effects and subjective preferenceJ Affect Disord2015180878925885065
9. Ybe Meesters & Marijke CM Gordijn (2016) Seasonal affective disorder, winter type: current insights and treatment options, Psychology Research and Behavior Management, 9:, 317-327, DOI: 10.2147/PRBM.S114906