Why You’re More Likely to Be Depressed in February – And How to Reverse It Quickly

Dr. Frank Shallenberger, MD

February 18, 2019



It’s February, and we’ve been in the darkest, coldest time of year for several months. For some people, this is a SAD time of year. I’m talking about SAD as in Season Affective Disorder. SAD is a condition that causes depression and anxiety during the times of the year when there’s less sunlight.

If you have SAD, the traditional treatment is to buy a bank of full spectrum lights to sit under every day. But, are there better ways to deal with the problem? Here’s what you need to know to avoid being SAD right now.

A review article entitled, “Vitamin D and Depression: Where is all the Sunshine?” gives us a good start on how to avoid SAD.

One of the obvious issues is vitamin D3. D3 is synthesized in the skin from cholesterol. The synthesis of vitamin D3 is stimulated by the ultraviolet light rays that we get from sunlight. Sunlight exposure accounts for over 90% of the vitamin D3 requirement for most people. So, one of the effects of decreased sunlight during the winter is decreased levels of vitamin D3. And, vitamin D3 deficiency is a problem for a lot of people.

The current estimates are that over one billion people worldwide have low vitamin D3 levels. And, to a large degree, low vitamin D levels may account for the mood issues that SAD brings on. One cross sectional study of 80 men and women aged 60 to 92 showed that more than half (58%) had abnormally deficient vitamin D3 levels. And, the lower the levels were, the more symptoms of depression they had.

There are two forms of vitamin D – D2 and D3. You’ll find D2 in plants, and D3 in animals. The liver converts both of them into the active form of vitamin D called 25-hydroxyvitamin D, although D3 converts into the active form more efficiently. So, the most effective form of oral vitamin D is D3.

What Is a Vitamin D Deficiency?

A deficiency of vitamin D is defined as a blood level of 25-hydroxyvitamin D less than 20 ng/ml. According to the authors of the article mentioned above, “Many studies have reported that low vitamin D levels may play a role in depression and possibly other mental disorders. And the research shows that SAD is directly related to vitamin D levels.”

They go on to quote one study that looked at 15 men and women with SAD. They gave half of them either a onetime dose of 100,000 units of vitamin D3 or timed exposure to ultraviolet light. The depression scores decreased from 10.9 to 6.2 in persons taking the vitamin D. Compare that to the men and women who had the light therapy. Their scores only decreased from 12.6 to 11.3.

The explanation is that for many people, for reasons that are not known, the process by which ultraviolet light stimulates vitamin D synthesis in the skin does not work very well. I’ll discuss why this is a little later. And, persons with SAD are not the only ones whose moods are affected by low levels of vitamin D.

You Don’t Have to Be SAD to Be Low in D

A 2008 study reported on over 1,200 men and women aged 65 and older. The researchers discovered that on average, vitamin D levels are 14% lower in persons with both minor and major depression. And, the lower the levels were, the greater the depression. So, how does that work?

Nobody really knows how sunlight and vitamin D affects mood, but it might have something to do with the direct action of vitamin D on the brain. Scientists have already discovered that there are vitamin D receptors in a part of the brain called the hypothalamus. The hypothalamus controls our hormonal system along with body temperature, hunger, thirst, fatigue, sleep, and you guessed it, psychological behavior. So, is vitamin D actually an anti-depressive treatment?

One study looked at supplementing a group of depressed patients with either 400 units of vitamin D3 or a placebo pill every day for one year. They found that the vitamin made no difference at all. But, that is a very small dose. And, the authors stated, “Results suggested that the dose of vitamin D may have been insufficient to cause a significant treatment difference between groups.” And, they are probably right.

Another study looked at the effect of a lot of vitamin D3, 20,000 units once or twice a week, on symptoms of depression in a group of overweight and obese men and women. They gave half of the patients a placebo. Compared to the placebo “there was a significant improvement in depression (using the Beck Depression Inventory) which was more pronounced in those with higher depression at baseline.” But, dose may not be the only factor.

Yet another study gave either 1,000 units of D3 or a placebo to a group of men aged 65 to 87 years. The results indicated that the D3 had no effect at all on general physical and mental health. However, here’s the potential problem. The men in the study were in excellent health and had sufficient levels of vitamin D before the study began. The odds are good that vitamin D supplements will only help with the symptoms of depression in people who have low levels.

So, What Causes Low Levels?

The most obvious factor is not getting enough sunlight. In this regard, the people most likely to have a deficiency are those who live in higher altitudes or in heavily overcast areas where there’s less overall sunlight. Another factor is not getting adequate sunlight exposure. Many people are so concerned about the negative effects of excessive sunlight on their skin that they go the other way and actually develop sunlight deficiency symptoms. Additionally, the use of sunglasses and sunscreen can result in lower vitamin D levels. But, decreased sunlight deficiency is not the only cause. There are other factors.

One of the most common reasons for vitamin D deficiency is birthdays. The older you are, the less efficient you are at synthesizing vitamin D. Additionally, women tend to be less efficient at making vitamin D than men. Dark skinned people are also less efficient. Another factor is obesity. The higher the body fat is, the lower the vitamin D levels. And this is interesting.

Researchers, knowing that sunlight, D3 supplements, nutritional supplements, and exercise are all effective treatments for SAD decided to do the obvious. They tested the results of doing it all. To do the study, they took 104 healthy women, aged 19 to 78. All of the women had mild to moderate depressive symptoms. Half of them did a brisk 20-minute outdoor walk five days per week, had daily light exposure, and also took a special vitamin supplement with B1, B6, B2, folic acid, selenium, and vitamin D3. The other half had the same treatment except that they were given placebo pills instead of the vitamins. Both groups improved over time on all measures, however, the improvement in mood, overall well-being, self-esteem, and happiness was significantly greater in the group that received all three treatments.

How Much Sunlight Do You Need?

It’s different for different people, but for most people, sun exposure to the arms and legs for five to ten minutes, two or three times per week during high sun hours, is enough. However, if you live in an area without much sunlight, you are likely to need more.

In terms of taking vitamin D supplements, here’s what I recommend. First, start taking 5,000 units of vitamin D3 every day. After two months, get your D3 and calcium levels checked. You should be shooting for a vitamin D level of 55 to 60 ng/ml along with a normal calcium level.

If you haven’t achieved that level, then keep increasing the dose until you do. And, don’t worry about toxicity. The studies are clear that there is no chance at all of vitamin D toxicity until the levels are at least greater than 150 ng/ml for months on end. But, do make sure to also check your blood calcium levels as you take higher doses of D3.

That’s because in certain individuals, especially those with marginal vitamin K levels, D3 supplements can drive up the calcium levels. And, that’s not a good thing. So, a good idea is to take some vitamin K along with the D3 to decrease the chance of this happening. Vitamin K activates MGP, a protein that helps direct calcium to the bones and away from undesirable places like the kidneys and the arteries. It also prevents an increase in blood calcium levels. For most people, taking 150-200 mcg of vitamin K in the form of MK7 will do the job.

So, if you are one of the many SAD people who tend to be moody in the winter months, keep these things in mind. The authors of the review study sum it up nicely, “If exercising outdoors in the sunshine, eating foods rich in vitamin D, and/or taking dietary supplements to improve vitamin D deficiency could improve one’s mental well-being, it would be a simple and cost-effective solution for many who are at risk for depression and possibly other mental disorders.”


Penckofer S, Kouba J, et al. Vitamin D and depression: where is all the sunshine? Issues Ment Health Nurs. 2010 Jun;31(6):385-93.

Health Nurs. 2010 Jun;31(6):385-93.


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