Recent literature has found a link between vitamin D deficiency and psychiatric illnesses, particularly depression. Several studies have shown that vitamin D supplementation can benefit depression symptoms. The goal of this e-Weekly is to review the literature and provide practical information for providers on using vitamin D supplementation as part of a depression treatment plan.
Observational data over the last 10 years has shown an association between vitamin D deficiency and chronic medical concerns, like depression, cancer and arthritis. Epidemiological studies have linked low vitamin D levels to schizophrenia and other psychotic disorders. In the United States, over half of psychiatric inpatients have vitamin D deficiency.
A person’s vitamin D status is determined by measuring 25(OH)D. Vitamin D insufficiency is defined as a 25(OH)D level of 21-29 ng/ml, and deficiency as <20ng/ml. Risk factors for vitamin D deficiency include insufficient sunlight exposure, obesity, gastrointestinal disorders, aging, renal disorders and use of certain medications (anticonvulsants and glucocorticoids). Vitamin D regulates expression of tyrosine hydroxylase, the rate-limiting enzyme in the biosynthesis of dopamine, norepinephrine, and epinephrine. This, along with other roles it plays in neurotransmission, suggests that vitamin D has a neurosteroid-like role in the central nervous system.
There are small studies that have had some interesting findings about the interaction between vitamin D deficiency and psychiatric illnesses. A group of small studies suggests that low prenatal vitamin D levels could increase the risk of schizophrenia for the child later in life. Another group of studies linked low vitamin D levels with impairments in cognitive functioning, including being more at risk for Alzheimer’s dementia and cognitive impairment related to depression.
Multiple studies have shown a link between low vitamin D levels and the presence of depression but it has been challenging to establish a causal relationship. Therefore studies looking at vitamin D supplementation as treatment for depression have mixed results. One randomized control trial showed that vitamin D supplementation significantly improved depressive symptoms including irritability and fatigue but another randomized control trial did not show a statistical difference compared to placebo.
Studies on vitamin D supplementation for seasonal affective disorder and other seasonal mood disturbances have more robust responses. Some studies showed an improvement in positive affect and a reduction in negative affect. Other studies showed a reduction in Beck Depression Inventory scores. This may have something to do with the complicated relationship among vitamin D, sunlight exposure and depression, because they appear to be linked. And when talking about ancillary treatments for depression, exercise, especially outdoor exercise which leads to additional light exposure and vitamin D exposure, can be an important consideration.
Treatment for vitamin D deficiency typically involves oral ergocalciferol 50,000IU per week for 8 weeks. If the vitamin D level has not sufficiently improved, consider a second course of ergocalciferol. Many experts also recommend daily supplementation for certain groups to prevent deficiency, including patients over the age of 70 and pregnant or lactating women.
In summary, those groups at risk for vitamin D deficiency include the elderly, adolescents, obese individuals and those with chronic illnesses. Interestingly, these groups are also at higher risk for depression. The role of vitamin D supplementation in treatment for depression has not been fully studied, but it could have a role as adjunctive treatment for milder cases or help with prevention of depression.