Is there a Link Between Vitamin D Deficiency and Depression?

Described as the “sunshine vitamin," vitamin D has steadily drawn public interest as a potential treatment for depression.

Could this inexpensive supplement counteract the effects of this widespread and, often, debilitating disorder?

While some research indicates that people with depression have lower levels of vitamin D than their counterparts without depression, so far, no large-scale study has found that the vitamin “cures” the condition.

The causes and symptoms of depression are multifaceted, which means that often no one drug, vitamin, or identified treatment can make them disappear entirely.

What Is Depression?

Major depressive disorder is a treatable medical condition that has a negative effect on an individual’s feelings, thoughts, or behaviors.

Symptoms of Depression

The following symptoms, among others, can be mild, moderate, or severe in intensity. People with depression may:

• Lose interest in activities they once appreciated
• Have trouble completing tasks
• Isolate themselves
• Find it difficult to sleep or eat well
• Experience suicidal ideation

The American Psychiatric Association estimates that the illness affects 1 in 15 adults (6.7%) in any given year and that 1 in 6 people (16.6%) will experience depression in their lifetimes.

Causes of Depression

The onset of depression typically occurs in late adolescence or early adulthood, and research indicates that depression runs in families.

People who have close (first degree) relatives, such as parents, siblings, or children, with depression have a significantly greater chance of developing the condition themselves.

In addition to genetics, biochemistry, environmental factors (a history of abuse or neglect), and personality (poor self-esteem or pessimism) are risk factors for the illness.

Women are more likely than men to develop depression. Among other factors, hormonal changes related to pregnancy, menstruation, and menopause increase the odds of developing the disorder. It is estimated that one in eight women will experience depression at some point in their lifetime.

What Is Vitamin D?

Also known as calciferol, vitamin D is a fat-soluble vitamin. This means that the body stores it in the liver and in fatty tissue.

While some foods, such as salmon, mushrooms, and egg yolks, naturally have vitamin D, other foods are fortified with the substance.

Vitamin D has several benefits, as it can help to prevent conditions such as rickets in children and osteomalacia in adults, and, along with calcium, it can prevent the elderly from developing osteoporosis.

It has also been linked to lower inflammation and the body’s regulation of immune function and glucose metabolism.

Some studies, with mixed results, have found that vitamin D supplementation can reduce the risk of individuals developing various forms of cancer and cardiovascular disease. Similarly, the link between vitamin D and depression also remains unclear. 

Research Studies

The National Institutes of Health’s (NIH) Office of Dietary Supplements reports that a review of 14 studies involving 31,424 adults found that low levels of vitamin D are associated with depression but that clinical trials don’t back up such findings.

A meta-analysis of nine trials involving 4,923 adult participants with depression did not conclude that vitamin D supplementation reduced symptoms of the disorder.

According to the NIH, “The trials administered different amounts of vitamin D (ranging from 10 mcg [400 IU]/day to 1,000 mcg [40,000 IU]/week). They also had different study durations (5 days to 5 years), mean participant ages (range, 22 years to 75 years), and baseline 25(OH)D level.”

The results of one of the largest studies to investigate the link between long-term vitamin D supplementation and depression were published in the Journal of the American Medical Association (JAMA) in August 2020.

This randomized clinical trial took place over five years and involved 18,353 adults aged 50 years or older who did not have depression or symptoms of it at the beginning of the study.

In the end, the researchers found no statistical difference in “the incidence and recurrence of depression or clinically relevant depressive symptoms” over the course of the study in the participants who took vitamin D compared to those who took a placebo.

Vitamin D Deficiency in People Who Are Depressed

Collectively, the research on vitamin D supplementation and depression indicate that there’s a correlation between the two but not a causation. In other words, while depressed individuals may have lower levels of vitamin D, that occurrence did not cause them to develop the illness.

If vitamin D deficiency were the cause, then supplementation to increase levels would likely have reduced the signs and symptoms of depression or prevented it. 

The fact many of the groups vulnerable to depression are also prone to vitamin D deficiency may be responsible for the correlation (not the causation) between the two.

According to a study called “Vitamin D and Depression: Where is all the Sunshine?,” the groups at risk for vitamin D deficiency “include the elderly, adolescents, obese individuals, and those with chronic illnesses." The researchers also stated that “it is these same groups that have also been reported to be at risk for depression.”

People With Depression May Spend Less Time Outside

Some of the symptoms of clinical depression, such as social withdrawal and eating difficulties, may play a role in vitamin D deficiency. When people socially withdraw, they’re not as likely to spend as much time in public, which means they may not get the sun exposure they need to make adequate amounts of vitamin D.

People with severe depression may have trouble even getting out of bed and those with milder forms of the illness may go from home to work and back again but rarely take part in outdoor activities.

Since social isolation can worsen depression symptoms, healthcare professionals advise people with the condition to spend time with others. In the process, they're likely to get more sunlight and raise their vitamin D levels.

People With Depression May Have a Poor Diet

Individuals grappling with depression also tend to have difficulty practicing self-cafe. This puts them at risk for not eating a balanced diet, as a depressed individual may not take the time to look for products fortified with vitamin D or to eat foods with naturally occurring amounts of the substance.

In short, individuals with the illness may unwittingly engage in behaviors that make them vitamin D deficient, but spending time outside with friends or practicing the self-care required to eat well can raise their levels of this valuable substance.