- Vitamin D receptors have been found in many parts of the brain. Some of the receptors are specific receptors for vitamin D. These receptors are found in the areas of the brain that are linked to the development of depression. Therefore, vitamin D has been linked with depression and with other mental health problems.
- One theory is that vitamin D affects the amount of chemicals called monoamines, such as serotonin, and how they work in the brain. Many anti-depressant medications work by increasing the amount of monoamines in the brain.
What does the research say about vitamin D and depression?
- A 2008 study from Norway showed that people with low levels of vitamin D in their blood had more symptoms of depression. The investigators also found that taking vitamin D in large amounts, improved the symptoms of depression indicating a possible causal relationship. The biggest effect was observed in people with more severe symptoms. However, the study only looked at people who were overweight, so it is not possible to conclude whether the results would be similar for everyone.
- A 2012 study from Norway investigated whether vitamin D blood levels were related to the symptoms of depression. The study also looked at whether taking a vitamin D supplement affected symptoms of depression in people with low vitamin D levels. The investigators found that: (1) low Vitamin D levels are linked to the symptoms of depression; (2) when people with low vitamin D levels took a supplement, their vitamin D levels improved but this had no effect on their symptoms of depression; (3) low vitamin D levels could be the result (and not the cause) of depression. The study used a sufficient dose of vitamin D supplement but for only six months. Because depression is a condition that develops slowly and slowly and causes persistent feelings of sadness and loss of interest; the study might have revealed different results if it was conducted for an extended period of time.
- A review of the research about vitamin D and depression published in 2013 analyzed all observational studies and randomized controlled trials about depression and vitamin D up until February 2011. The investigators found more than 5,000 research articles; however, only 13 explored this area effectively. Over 31,000 people participated in these 13 studies. The results showed that there is a relationship between low levels of vitamin D in the blood and depression. However, the research did not show whether vitamin D was the cause or effect of depression.
- A 2014 study of young adults in New Zealand found that vitamin D is a predictor of depression symptoms — there was a modestly higher depression score for those with lower vitamin D levels. However, there was no difference in the time spent outdoors between those with a lower or higher depression score.
- A 2014 study in China investigated the relationship between Vitamin D and post-stroke depression (PSD). The study found that six months after an ischemic stroke, those with vitamin D levels below 11 ng/mL had a much higher prevalence of depression.
- A 2014 study in Sweden found that suicide attempters were deficient in vitamin D. They also had higher concentrations of pro-inflammatory cytokines, which have been observed in other suicidal patients. Vitamin D is known to reduce the levels of pro-inflammatory cytokines.
- A 2014 study in The Netherlands involving 1,102 people with current depressive disorder and 790 people with former but not current depressive disorder found lower vitamin D levels among those with current depressive disorder and lower symptom severity for those with higher vitamin D levels. There was also a significant correlation between vitamin D status and developing depressive symptoms at a 2-year follow up suggesting that Vitamin D could be a cost-effective as part of preventive or treatment interventions for depression.
- A 2015 study in Finland found a strong correlation between depressive disorder and vitamin D levels — those with vitamin D levels above 22 ng/mL (56 nmol/L) had a 35% lower risk of depressive disorder than those with vitamin D levels below 14 ng/mL (34 nmol/L).
In summary, studies show that there is a link between vitamin D and depression. However, we do not know exactly what that link is. It has also not been established whether low levels of vitamin D cause depression, or whether depression causes low levels of vitamin D. We are not certain whether taking a vitamin D supplement, or getting more vitamin D by exposing the skin to the sun, will help to prevent or ease the symptoms of depression in some people.