Impact of Vitamin D Deficiency on Mental Health

Vitamin D is not just a nutrient; it’s a hormone with receptors in nearly every cell and tissue of the body. It is estimated that about 3% of the human genome is regulated by the vitamin D endocrine system and over 1000 genes in the human body are impacted. Vitamin D has a wide range of impact on systemic health and has been shown to support physical, mental and immune system function. 

Correlational scientific evidence consistently indicates that vitamin D status is inversely related to mental health issues, including depression and anxiety in all age groups. Research suggests that vitamin D can impact mood and psychiatric disorders. Some studies have suggested that vitamin D deficiency may worsen psychiatric symptoms in individuals with depression and bipolar disorder. Given this evidence, raising vitamin D level through endogenous methods appears to be useful in improving multiple mental health markers. However, taking oral vitamin D supplements does not show similar results with any consistency. This is likely due to the very different way the body uses sunlight to produce endogenous hormones, like vitamin D, compared to exogenous forms. This is significant given that the Centers for Disease Control and Prevention found that 9.1% of adult Americans met the criteria for depression, and current treatment options are limited, have imperfect benefit, and pharmacologic solutions carry side effects.[1] 

Can vitamin D deficiency cause mental health problems?

Several published reviews indicate that vitamin D plays a role in the pathogenesis
of mental health disorders and particularly mood disorders. When looking at the general population, lower levels of vitamin D are found in people with depression as well as in those with anxiety disorders, regardless of age or gender.[2] Serum vitamin D also appears to be associated with severity of depressive symptoms. While other factors may contribute to how the sun benefits mental health, the evidence for a vitamin D specific influence is compelling. Vitamin D is a neurosteriod hormone in the brain that exerts its biological function not only by influencing cellular processes directly, but also by influencing gene expression through vitamin D response elements.

Can vitamin D deficiency cause mental confusion?

Vitamin D receptors are found throughout the brain. Vitamin D deficiency is linked to mental health symptoms and low vitamin D impacts mental health through a variety of mechanisms. Vitamin D can impact mood and psychiatric disorders, and research suggests that vitamin D deficiency may worsen psychological symptoms. Vitamin D supports mental focus and vitamin D deficiency can cause altered mental health status. Research suggests that low levels of vitamin D can lead to mental confusion and some people with vitamin D deficiency experience mental fog. 

What does vitamin D do for mental health?

The complete impact that sun exposure has on mental health cannot be replicated by exogenous vitamin D supplementation. The benefits of sunlight for mental health are more than vitamin D3 production alone.

The measure of vitamin D in the blood is often simply a biomarker for UVB sun exposure,
so while researchers are trying to correlate vitamin D levels with various outcomes, they are often excluding other UV-related factors that could be relevant. In particular, evidence shows that skin exposure to the UVB portion of the sun’s spectrum affects the hypothalamic pituitary adrenal (HPA) axis which leads to the production of mood enhancing hormones like beta endorphin. 

• One study found that after a 12-week behavioral activation program emphasizing safe-sun exposure, subjects in the intervention group had significantly higher serum vitamin D and significantly lower depression scores compared to controls.[7]

• A placebo controlled trial found a highly significant improvement in both depressive and cognitive symptom scores in dermatologic patients and a non-significant tendency towards improvement in healthy volunteers after exposure to UVB light.[8] 

• A study of 20 healthy women without depression found well-being mood state improved after three full-body ultraviolet exposures during the winter.[9] 

• A study measuring mood variables in subjects with fibromyalgia syndrome, found six ultraviolet exposures resulted in a positive effect on well-being, relaxation, and reduced pain levels.[10] 

UVB and Vitamin D mental health benefits

Studies have shown that increasing vitamin D is good for mental health and mood disorders. Intervention by controlled UVB exposure can be used to stimulate multiple mechanisms of action that have a systemic effect on mental health.

HPA Axis 

The hypothalamic pituitary adrenal (HPA) axis is a dynamic intertwining of the central nervous system and endocrine system in response to stress. Stressful life events and dysfunctional HPA axis have been implicated in mental health pathogenesis, including mood and anxiety disorders. The hypothalamus plays a key role in the symptoms of depression, such as disordered day-night rhythm, lack of reward feelings as well as disturbed eating, sex, and cognitive functions. The skin has a systemic impact on the HPA axis when exposed to the UVB region of ultraviolet light, but not the UVA region.[11, 12] In vitro and animal studies have shown that skin exposure to UVB light expresses all elements of the HPA axis including corticotropin-releasing hormone, proopiomelanocortin, adrenocorticotropic hormone, beta endorphin with corresponding receptors, the glucocorticoidogenic pathway, and the glucocorticoid receptor.[11] 

Beta Endorphin 

Beta endorphin is primarily utilized in the body to reduce stress and pain. This peptide hormone is at least 17 times more potent than morphine, meaning that even small increases in the body can have a profound effect.[13] Research links beta endorphin to major depressive disorder and theorizes that HPA axis dysregulation may account for depressive symptoms in some individuals.[14-16] Specifically, research shows that individuals with depression may have reduced beta- lipotropin-beta-endorphin response. One study found depressed patients displayed significantly lower beta endorphin plasma levels than controls at baseline and after two tests designed to measure Adrenocorticotropic hormone dysfunction.[16] Additionally, data indicates that after two weeks of treatment, increased blood plasma level of beta endorphin in patients with depression correlates with positive response to therapy.[17] 

It is documented in vitro and in vivo that the UVB spectrum of sunlight causes the production of beta endorphin in the skin. It has been suggested that beta endorphin release after UVB exposure may be an evolutionary reward system for sunlight exposure that is powerful enough to be the biochemical mechanism responsible for tanning “addiction”. In vivo studies have proven that, similar to vitamin D production, the UVA spectrum does not induce an increase in serum beta endorphin.[18] 

Serotonin

Serotonin influences a vast number of brain cells that are related to mood, sexual desire, appetite, sleep, memory and learning, temperature regulation, and social behavior. Many researchers believe that an imbalance in serotonin may lead to depression. Serotonin imbalance may stem from low brain cell production of serotonin, a lack of receptor sites able to receive the serotonin that is made, inability of serotonin to reach the receptor sites, or a shortage in tryptophan, the amino acid from which serotonin is made. It is for this reason that selective serotonin reuptake inhibitors (SSRIs) are widely prescribed to treat depression. 

Experiments have shown that calcitriol, the active form of vitamin D, mediates gene transcription in the brain that acts not only to induce serotonin synthesis, but also inhibits reuptake, likely elevating serotonin in the central nervous system.[19,20] Some researchers believe that optimizing vitamin D may help prevent and modulate the severity of brain dysfunction. Literature indicates a link between sunshine and serotonin due to their concurrent seasonal fluctuations.[21] A study of 101 subjects showed the rate of serotonin turnover in the brain was lowest in winter and the rate of serotonin production was directly related to the duration of bright sunlight exposure.[22] Another study of 36 healthy subjects found that low sun exposure was correlated to a 20 – 30% reduction in serotonin receptor-1A binding in limbic regions of the brain, shown to increase dopamine release.[23]