As we write this, it’s the depths of winter here in Michigan. It’s been exceptionally cold and extremely snowy this year, with low-hanging gray clouds, wind stripping any warmth you have when you brave the elements, and there’s even an unusually fierce strain of the flu going around.

In other words, it’s been pretty awful for seasonal depression.

We’ve been talking about seasonal depression a lot lately, but something we’ve mostly only mentioned in passing is the association with vitamin D. Today, we wanted to take a closer look at the science, why people think vitamin D can help with seasonal depression, and whether or not there’s any truth to it.

DISCLAIMER: This article is for informational and educational purposes only and should not be considered medical or psychological advice. The information presented here is not intended to diagnose, treat, cure, or prevent any mental health condition or replace professional therapeutic care. Every individual's experience with trauma and mental health is unique. Please consult with a qualified mental health professional, therapist, or healthcare provider to determine the most appropriate treatment approach for your specific situation. If you are experiencing a mental health crisis or emergency, please contact your local emergency services or crisis hotline immediately.

What Causes Depression and SAD?

Let’s start with the million-dollar question: what causes depression?

The answer is: we don’t know.

Depression, including Seasonal Affective Disorder (SAD), is a very complex illness. There are biological elements, environmental elements, psychological elements, and even social elements, and two people who are essentially identical can experience different levels of depression entirely.

Unfortunately, modern medical science doesn’t really know what causes depression. We know some trends and commonalities in people who have depression that are less common in people without it. But, treating or addressing those commonalities only does so much to help.

This is part of why depression is such a difficult illness to treat, and why antidepressant medications can only do so much, while also not necessarily working for everyone.

Is Vitamin D Linked to Depression or SAD?

Why does vitamin D enter the conversation?

One of those common factors in people who have depression, especially winter-pattern seasonal affective disorder, is low levels of serotonin in the brain. Serotonin is a neurotransmitter that carries messages that regulate a lot of different bodily functions, including sleep, digestion, wound healing, blood clotting, libido, and mood. When it’s out of balance, both too low or too high, it causes problems.

Vitamin D is used for a lot of different purposes throughout the body as well. One of those purposes seems to be regulating serotonin levels. At least, that’s the theory, though relatively little evidence has actually been compiled to prove it. It’s one of those areas of medical science that is currently undergoing study, but results take a long time to gather.

What we do know is this:

• People with seasonal depression tend to have lower levels of serotonin.
• People with lower levels of serotonin tend to have lower levels of vitamin D.
• Seasonal depression tends to be more common in latitudes further from the equator, where days are shorter in winter.

You get some vitamin D from your diet, but the majority of the vitamin D in your body is synthesized naturally in response to sunlight exposure. Shorter days with more cloud cover mean less sunlight, which means less vitamin D.

If the theory is true, that means lower levels of vitamin D cause lower levels of serotonin, which contributes to depression.

Evidence For and Against Vitamin D’s Relation to Depression

There are also a couple of pieces of evidence that support this conclusion.

For one thing, there’s a second neurotransmitter in play as well: melatonin. Melatonin is the “sleep hormone”, the molecule your body produces to encourage sleep and help make sleep more restful. People with seasonal depression, in addition to having lower than normal serotonin, often have higher than normal melatonin.

Vitamin D also helps regulate melatonin by keeping it in check. The lower your vitamin D, the higher your melatonin tends to be. This further indicates some link between the three.

A second piece of evidence is that one of the most effective treatments for seasonal affective disorder is light box therapy. Light box therapy uses a bright light source that mimics sunlight, which convinces the body to produce more serotonin.

One flaw here, though, is that these light boxes don’t actually trigger the synthesis of vitamin D. Vitamin D is created in response to UV light, and light boxes explicitly avoid UV light, because it’s what causes sunburns, skin cancer, and other harmful side effects.

A handful of studies have been performed over the years on whether supplementing vitamin D can help treat depression and seasonal affective disorder. Results have been inconclusive. Some studies show benefits on par with a light box, while others show no change at all. One of the biggest and best trials performed to date found no significant change from supplementing vitamin D.

One problem, though, is that these studies take time to perform, and one of the key characteristics of seasonal affective disorder is that it changes over time. If you start a study and symptoms improve, is it because of the treatment, or just because winter is ending and spring is starting? It’s hard to say.

One thing we know for sure is that supplementing vitamin D is not a cure for depression. If it were, we definitely would know by now, and it wouldn’t be a problem anymore. Unfortunately, depression is too complex an illness to be treated so easily.

Is it Safe to Supplement Vitamin D?

Common advice for addressing seasonal depression is to take vitamin D, because even if it doesn’t help all that much, it won’t really hurt, or so common wisdom goes.

The truth is a little trickier. Vitamin D isn’t harmful in normal levels, but taking too much of it for too long can lead to a condition called hypercalcemia. Hypercalcemia causes a variety of problems, ranging from nausea and vomiting to frequent urination to bone pain and kidney stones. In extreme levels, it can even be fatal, though it takes a lot of vitamin D to reach that point.

It’s generally recommended for adults to get around 15 mcg (or 600 IU) of vitamin D per day. Children need a little less, and the elderly need a little more, but it’s in that range.

The tolerable upper limit for vitamin D intake for adults is 100 mcg (4,000 IU) per day. This level can cause the early symptoms of vitamin D toxicity, like nausea, particularly if your natural vitamin D is high or you’re getting a lot from diet or sunlight.

Many standard vitamin D supplements are around 50 mcg (2,000 IU) and are available in pharmacies across the country. There are smaller dose versions (about half that) and larger (as much as 125 mcg, or 5,000 IU) available as well.

In people who have a diagnosed vitamin D deficiency, your doctor might recommend even higher doses. For example, they might prescribe a 10,000 IU daily pill, or as much as a 50,000 IU weekly pill. These are fine for short-term treatment of deficiency, but are not meant to be taken long-term outside of extremely specific medical cases.

Do be aware that taking vitamin D supplements can interact with other medications. In particular, statins, steroids, diuretics, and anything that affects blood calcium levels can all change how they function when you’re taking vitamin D.

Here in Michigan, in the depths of winter when the days are short, and the sun is hiding, many people take a vitamin D supplement just to feel a little bit better. Even if it’s not going to cure depression, it’s not going to hurt as long as it’s in reasonable amounts.

Dealing with Depression and SAD in a Michigan Winter

We get it: winters are hard. Standard depression is often made worse by all of the same factors that trigger seasonal affective disorder, with the two being closely related in presentation and symptoms.

The good news is, treatment is available. Help is out there, and we’re happy to assist you.

In a Crisis? Seek Immediate Assistance

Before getting started, it’s important to recognize that assistance of all kinds is available.

Low levels of depression, low moods, and minor SAD can be treated, but so, too, can major depression and serious episodes.

• If you’re unable to get out of bed in the mornings
• If you’re experiencing active thoughts of self-harm or suicide
• If you can’t function in your daily life
• If you’re unable to care for your basic needs
• If your mood is shifting rapidly

Seek crisis care. You can call or text 988 to reach the Michigan Crisis and Access Line. MiCAL is completely free, completely confidential, and available 24/7 to help with your crisis. They can talk you through the immediate crisis, they can mobilize a crisis response unit, and they can help you connect with additional assistance for long-term treatment, no matter what your needs.

Get a Blood Test to Check Vitamin D Levels

If you’re considering vitamin D as a way to treat winter blues, seasonal affective disorder, or depression, it’s often a good idea to get a blood test. While you can take vitamin D supplements on your own (they’re readily available over the counter), it can be nice to know what your vitamin D levels are.

Here in Michigan, there’s a pretty good chance you have at least some level of vitamin D deficiency. A study from 2010 found that as much as 75% of patients in Michigan had clinical vitamin D deficiency, and estimates place the rate of some level of deficiency at around 50% of Michigan’s population, particularly in winter.

The blood test can also show if any related vitamins or minerals are too low or too high, and it gives you a baseline you can measure later to tell if the vitamins are having an effect. It can also check to see if your calcium levels are high, which can make vitamin D supplements riskier.

Getting a blood test is usually pretty easy. They’re routine medical procedures, and you can usually ask for one directly through a system like MyChart or through a phone call with your doctor. You may not even need an appointment, or you can use a video appointment.

Talk to Your Doctor About Vitamin D Supplements

If your levels of vitamin D are very low, your doctor might prescribe you high-power vitamin D supplements. If they’re only a little low, they may recommend smaller daily supplements. The results of the blood test can also be reviewed to check if you have any other symptoms of underlying illness that could be addressed at the same time.

It’s important to talk to your doctor about vitamin D supplements, especially if you’re on other medications. Medication interactions can be dangerous, so your doctor will want to know what you’re taking so they can give you an appropriate course of action.

Seek Psychotherapy for Depression

While vitamin D might be able to help you feel better in a few different ways, the link between vitamin D and depression or SAD is mixed. Fortunately, one form of treatment has been proven repeatedly: psychotherapy.

In particular, talk therapy methods like cognitive behavioral therapy and dialectical behavioral therapy are some of the most effective treatments for depression we know of. Additionally, some evidence has been growing to suggest that eye movement desensitization and reprocessing (EMDR) therapy can also be effective for certain kinds of depression.

At BMC-Troy, we’re proud to offer all of these treatment options and more. Located right here in Troy, we serve many people throughout metro Detroit, and we’re ready to help you stave off the winter blues as well. To get started, you can fill out our new patient intake form online. Give us a call at 248.528.9000 with any questions.

Consider and Discuss the Possibility of Antidepressants

For severe or treatment-resistant depression, you might also consider antidepressant medications. These medications have a more direct impact on serotonin in particular, and can be very effective for many people, alongside therapy in particular.

It can also be important to adjust your medication according to changes in your mood. When winter is at its darkest and depression is fierce, we can help with medication management to keep you in balance. All of this will be discussed with our practitioners when you visit us for the first time.

You deserve treatment and the chance to enjoy what a Michigan winter has to offer, so we encourage you to reach out for the help that’s available.