Does vitamin D really help with seasonal affective disorder?

It rained here last week. The citizens of San Diego exchanged sun glasses and sandals for long forgotten umbrellas, galoshes and rain coats as clouds covered our usually sunny sky. Traffic jams, car accidents and mayhem ensued. I kid you not when I say that one of the local meteorologists actually said “stay tuned for team coverage of the rain” with “updates every minute.” Over the course of 48 hours, San Diego got hit with just under two inches of rain. During our deluge, a morning news anchor said he thought the clouds were bringing people down and that maybe the city was being hit with seasonal affective disorder (SAD). I am pretty sure a producer spoke into his ear piece after he made that comment because he paused, awkwardly, and then clarified that SAD is a real medical disorder. The news anchor’s careless comment got me thinking about SAD, sunlight and vitamin D. So, I decided to do some reading and write about it this week.

Fall in San Diego (October 1, 2014)

A brief overview of seasonal affective disorder (SAD)

Seasonal affective disorder is a specific form of depression. It is triggered by the changing of the seasons. There are two types of SAD. Fall/winter SAD begins in the fall or winter and lifts in the spring or summer. It is the most common form of SAD. Some people experience an opposite type of SAD called spring/summer SAD. This version of SAD begins in the spring or summer and ends in the winter. According to the American Academy of Family Physicians, 4% to 6% of people in the United States live with SAD. Women tend to be diagnosed with it more frequently than men, although men may have more severe symptoms. SAD can develop at any age, but the most frequent age of onset occurs between 18-30 years of age. 

Resources:

• Mayo Clinic: Seasonal Affective Disorder

• American Academy of Family Physicians: Seasonal Affective Disorder

• Family Doctor.org: Seasonal Affective Disorder

What causes SAD?

Scientists do not know what causes SAD. The following factors are believed to contribute to it.

Season changes, altered sunlight and circadian rhythms

The amount of sunlight you are exposed to changes with the seasons. During winter, daylight hours become more limited. Some people may experience a shift in their circadian rhythm (biological clock). The shift may impact mood, hormones and sleep patterns which may trigger depression. 

Melatonin

Melatonin is a hormone produced by the pineal gland. It is produced with the onset of nighttime (darkness) and facilitates sleep. It is possible that as the amount of daylight and darkness change with the seasons, the amount of melatonin produced by the body gets out of whack, at least for some people. Melatonin affects mood and sleep. Symptoms of SAD include, among other things, altered mood and disordered sleep. 

Serotonin

Neurotransmitters are chemicals that communicate messages from one nerve cell to another. Serotonin is a neurotransmitter that has been linked to depression and mood. Serotonin reuptake inhibitors are a type of medication used to treat depression. Serotonin is produced in the gastrointestinal tract and in the brain. 

Resources:

• Mayo Clinic: Seasonal Affective Disorder

• Family Doctor.org: SAD

• Medline Plus: SAD

• Cleveland Clinic: Seasonal Affective Disorder

• American Psychiatric Association: Seasonal Affective Disorder

Vitamin D

The human body has the ability to synthesize vitamin D in response to sun exposure (specifically in response to the UVB rays). However, lots of things can interfere with this ability. Below is a list of factors that influence vitamin synthesis. This list is modified from the  Nutrition Tuesday - Vitamin D and Alzheimer's Disease post.

• Skin tones with more melanin require more time in the sun (lighter pigments need about 10-15 minutes, darker pigments may need 30 minutes to make the same amount of vitamin D)

• Sunscreen (SPF 8 and above inhibits vitamin D synthesis by blocking UV rays)

• Smog, fog, cloud cover, shade (reduces UV by 50-60%) 

"SmogNY". Licensed under Public domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:SmogNY.jpg#mediaviewer/File:SmogNY.jpg

• Clothing (blocks exposure – light knits may allow some exposure)

• Glass (UV rays that lead to vitamin D synthesis do not penetrate windows – being inside means no exposure)

• Time of year (very limited to no UV exposure for some regions during fall and winter)

The body needs vitamin D to in order to absorb dietary calcium, to maintain blood calcium and phosphorus levels, to mineralize bone, and to form and remodel bone. 

Vitamin D also has other important functions in the body. It is involved in cell signaling and in gene transcription. There are vitamin D receptors (VDR) in cells that need vitamin D. Once vitamin D enters a cell, it binds to a VDR. The vitamin D-VDR complex travels to the cell's nucleus. In the nucleus, the vitamin D-VDR complex binds to specific regions of the DNA called vitamin D response elements (VDRE). Other transcription factors and hormone complexes also bind to the DNA and interact with the vitamin D-VDR complex. There are thousands of VDREs throughout the genome. Vitamin D is used in lots of places to regulate gene transcription.

Resource

• Office of Dietary Supplements: Vitamin D (for Health Professionals)

Vitamin D and SAD in the news

Here are a just a few of the online news reports about vitamin D and seasonal affective disorder. I found these between December 1, 2014 and December 8, 2014. 

• University of Georgia: College of Education News

• UGA - Press Release / News Article Vitamin D and SAD

• Science News - UGA, Vitamin D and SAD with UGA cited

• Medical News Today: Researchers link vitamin D deficiency to seasonal affective disorder

• Disabled World: Vitamin D Deficiency Linked to Depression and SAD

• Bustle: Seasonal Affective Disorder Is Linked to Vitamin D Deficiency, So Here's How to Fight the Winter Blues

• Inquisitor: Vitamin D Deficiency Causes Depression and SAD

If you check any of these out (any of them), it will become clear that they all refer to the same research group and present the researchers' work with varying degrees of "doneness." Some of these reports suggest that researchers conducted a study and discovered that vitamin D can treat or cure SAD (wrong!). Others (correctly) reported or at least implied that the researchers developed an idea based on a review of the literature about vitamin D, SAD, and depression. 

The scientific paper that all of this is about was published in the journal Medical Hypotheses online in September  then in print November 2014 (Stewart, Roecklein, Tanner, & Kimlin, 2014). I fail to understand why the online news writers picked up a feature that consists of a literature review and a hypothesis. This scientific paper is, by nature, not newsworthy. It cannot be because it is a review paper. It is an organized, thematic, synthesized discussion of the available scientific literature on a given topic. A review paper is like the first chapter of a dissertation or master’s thesis. It is like the beginning of a grant proposal. Every scientist has to conduct and eventually write some form of a literature review as part of the rationale for their research. Literature reviews are great resources and reading for people working in the related discipline. Literature reviews are not primary research articles. They are not cutting edge science and they should not be treated as such.

Reference

Stewart, A. E., Roecklein, K. A., Tanner, S., & Kimlin, M. G. (2014). Possible contributions of skin pigmentation and vitamin D in a polyfactorial model of seasonal affective disorder. Med Hypotheses, 83(5).

Highlights from the literature review

• Vitamin D is synthesized in response to the sun. It is normal for vitamin D levels to fluctuate with seasons. People tend to have their highest levels of vitamin D at the end of summer and their lowest levels of vitamin D in late winter.

• SAD is a type of depression related to changes in the season and it is linked to alterations in light and dark hours to which the body is exposed.

• Circadian rhythms are regulated in the brain. 

• Vitamin D response elements (VDREs) are found in regions of the brain that are involved in the expression of genes that influence circadian rhythms. 

• Vitamin D receptors are also found in regions of the brain involved in processing signals that pertain to the daily internal clock (circadian rhythm). 

• The hypothalamus is a part of the brain that contains a lot of vitamin D receptors and has the capacity to take inactive forms of vitamin D and activate them. The hypothalamus may be an important site for vitamin D activity and the regulation of circadian rhythms (Stewart, Roecklein, Tanner, & Kimlin, 2014) .

• Research has demonstrated that serotonin levels vary with the seasons and that there is less serotonin circulating in the body during the fall and winter months than compared to the spring and summer months. Dopamine production may also be impacted by vitamin D (Praschak-Reider, Willeit, & Wilson, 2008).

• VDREs have been located on two genes that are involved in the synthesis of serotonin (Cass, Smith, & Peters, 2006).

• Serotonin is a precursor to melatonin. Melatonin levels increase with darkness (the onset of evening hours). More melatonin may be produced during the longer dark periods that occur during the winter months.

• Vitamin D deficiency may be associated with an increased risk of depression but results are mixed as to whether or not vitamin D treatment helps improve symptoms of depression (reviewed by (Stewart et al., 2014).

• Darker skin contains more melanin. It takes longer for UV rays to penetrate melanin and trigger the production of vitamin D, therefore people with darker skin require longer sun exposure to make the same amount of vitamin D as people with lighter skin. Biologically, having more melanin confers greater protection from the sun because it protects the skin from damage that can be caused by UV rays. However, upon moving away from a more equatorial location to places of higher latitude, people with darkly pigmented skin may be at greater risk of vitamin D deficiency. 

The researchers’ hypotheses

After reviewing the literature, the researchers developed two hypotheses regarding vitamin D, SAD, and skin pigmentation. Their hypotheses apply to people with dark skin (high melanin content) that have moved to regions of high-latitude (farther from the equator).

• The first generation: They hypothesize that the first generation of dark-skinned migrators that move to more northern regions are more likely to experience acute bouts of SAD. The researchers hypothesize that the first generation will respond well to vitamin D treatment along with other traditional treatments like phototherapy (light therapy) because they are overtly vitamin D deficient.

• The second generation: They also hypothesize that the children of first generation migrators are at greater risk of lifetime complications that result directly from exposure to inadequate vitamin D during gestation and the post-natal period.

• Cells need vitamin D in order to grow, specialize, and undergo programmed cell death. Vitamin D is also needed for the growth of nerve cells, for the production of serotonin and dopamine. 

• The authors suggest that inadequate vitamin D exposure during gestation and infancy directly contributes to the lifetime problems experienced by second generation children. The problems these children face may include disorders that are psychological, developmental, and emotional in nature.

References

Stewart, A.E. Roecklein, K.A., Tanner, S, & Kimlin M.G. (2014). Possible contributions of skin pigmentation and vitamin D in a polyfacotrial model of seasonal affective disorder. Med Hypotheses, 83(5), 517-525.

Praschak-Rieder, N., Willeit, M., Wilson, A.A., Houlse, S., & Meyer, J.H. (2008). Seasonal variation in human brain serotonin transport binding. Arch Gen Pyschiatry, 65(9):1072-8.

Cass, W. A., Smith, M. P., & Peters, L. E. (2006). Calcitriol Protects against the Dopamine- and Serotonin-Depleting Effects of Neurotoxic Doses of Methamphetamine. Annals of the New York Academy of Sciences, 1074(1), 261-271. 



Final Thoughts

• At this time, no evidence exists to support the use of vitamin D supplements to cure, treat or prevent SAD or depression.
• This research group has written a comprehensive literature review and proposed a hypothesis that could (should) direct future research projects. 
• Despite the tone of the university's press release and the online news reports, researchers have not yet published the results of a research study.
•  All of the press about this paper leads me to believe that none of the journalists read or even glanced at the actual paper that was published in Medical Hypotheses. This practice spreads misleading, incomplete and wrong information faster than a California wildfire.