Depression is one of the most common mental health issues in the world. It is believed that some 11.23% of people in the western world suffer from this condition. Interestingly, geographical location seems to play an important part in the rates of depression. In more northern parts of the world, depression rates seem to be much higher. This has led to some scientists questioning whether there is a link between depression and vitamin D.
What Is Depression?
Depression is about more than feeling sad, miserable or fed up. It is about having these feelings for a long period of time, without noticing any improvement even if you talk about them. Depression can be mild, but it can also be very severe. The more severe the depression, the more life-limiting it is as well.
Causes of Depression
While seen as a mood disorder, depression is actually a biological disease. It also has genetic characteristics. A number of things can trigger the onset of depression, which are usually traumatic or sad events. However, different people respond differently to various situations. The most common trigger events, include:
• A major life change – job change, divorce, death of a loved one, house move, etc.
• Physical illnesses, particularly hormonal ones like hypothyroidism, and also painful conditions like arthritis, or life-threatening conditions such as cancer
• Personal circumstances – loneliness and stress are two common triggers
• Family history – there is strong evidence to suggest that depression runs in families
• Personality – some people just seem to be more likely to become depressed This could be genes, but it could also be relating to early life experiences
• Too much alcohol
Vitamin D and Depression
Vitamin D is necessary in our body primarily to enable the absorption of calcium and phosphorus. However, it also functions in a range of other roles. It is known that the brain has many vitamin D receptors, particularly on the surface of cells. This is where chemical signals originate from and travel to. While it is not known exactly what vitamin D does in the brain, the fact that receptors are there means that it might have a role to play in depression.
Scientists have theorized that vitamin D may affect the levels of monoamines, which are chemicals like serotonin. Most antidepressant medications work by increasing the levels of monoamines in the brain. It is possible, therefore, that vitamin D plays a similar role.
Because vitamin D is now known to do so many different things, more and more research are also being conducted about it. However, these studies are very recent and therefore are still quite limited. As a result, preliminary tests have come up with some conflicting issues. This is probably because different scientists use different parameters. Unfortunately, this means that any of the conclusions that have been drawn by scientists are not yet set in stone. Nevertheless, this does not make them any less interesting. So far, we know that:
• In 2013, scientists reviewed a wealth of studies that had been conducted on a possible link between vitamin D and depression up until February 2011. Over 5,000 research articles existed, but just 13 really looked at vitamin D and depression. This did mean that scientists had evidence collected from some 31,000 different people. These particular studies showed that there is a link between depression and vitamin D. What wasn’t clear, however, was causality – did low vitamin D levels cause depression, or did depression cause vitamin D deficiency? These questions remain unanswered as of this time.
• In Norway in 2008, researchers found that people with a vitamin D deficiency suffered from more depression symptoms. They also found that high levels of vitamin D supplementation improved these symptoms, particularly in people who had the most severe depression symptoms. Unfortunately, all participants in this study were overweight. This meant that it was not clear whether the same results would apply to healthy weight people. Additionally, a calcium supplement was also given, and this could mean that it is was actually the calcium that improved symptoms, or perhaps the combination of the two.
• There is strong evidence to suggest rates of depression rise during winter months.
• A study in Norway looked at whether there was a link between vitamin D blood levels and depressive symptoms. It then provided people with a vitamin D supplements to see whether there was an effect. This was perhaps the most interesting study, with a number of key findings:
People who have low levels of vitamin D experience more depressive symptoms.
People with low levels of vitamin D and depressive symptoms did not notice an improvement in their depressive symptoms through vitamin D supplementation, although their levels of vitamin D did rise.
Rather than causing depression, low vitamin D may be a result of depression.
While this particular study was very interesting, it only looked at a six month period. This is effectively not a long enough period of time to draw any permanent conclusions, particularly because people tend to suffer from depression for much longer than that.
• A New Zealand study in young adults showed that those who had lower levels of vitamin D had a slightly more frequent incidence of depression.
• In China, a study looked at people who suffered from an ischemic stroke, which is the result of a blood clot. They found that if people also had low vitamin D levels in their blood, they were more at risk of developing depression.
• A Swedish study found that suicidal patients had much lower levels of vitamin D than patients who suffered from depression but weren’t suicidal, or people who didn’t suffer from depression at all. However, they also had higher cytokine levels, which are pro-inflammatory, something that has previously been linked to suicidal thoughts and behaviors. Vitamin D has been shown previously to lower levels of cytokines.
• A study in Iowa that took place over a 20 year period concluded that people who suffered from major depressive disorder had an increase in their symptoms in winter months, with the peak being in March. They also found that new depressive episodes were most common between October and January, with the peak in January.
• A Dutch study that looked at 1,102 subjects all aged between 18 and 65, who all had current depression, as well as at 790 subjects that had suffered from depression in the past but not currently, found that the current depressed people had less severe symptoms if they had higher levels of vitamin D. It also found, at a two year follow up, that there was a correlation between the development of depressive symptoms and status of vitamin D.
• A Finish study found a very significant inverse correlation, looking specifically at depressive disorder and status of vitamin D. Those who had higher levels of vitamin D had 35% less chance of developing a depressive disorder. However, this was a cross-sectional study, which means the results are not very strong.
Depression in Women and Vitamin D
Of particular interest is the fact that there have been a number of studies that looked specifically at depression and vitamin D in women. Notable studies include:
• A local study published in 2012 did not find a correlation between taking vitamin D supplements and lowering depressive symptoms. It was the first study to look into this issue, but they only used a 400 IU supplement, which is very low. Additionally, participants also took a calcium supplements, which may have affected the result.
• The same year, older women were tested and it was found that providing them with a vitamin D supplement did not improve symptoms of depression. The same results were found with those women who were also given hormone therapy.
• A Japanese study looked at pregnant women and found that those who had good levels of vitamin D were 50% less likely to develop depression.
What Do We Know?
• It seems that there is a link between low vitamin D levels and depression, but what that link is, is not clear yet.
• A low vitamin D level may cause depression, but it is as likely that vitamin D levels drop because of depression.
• Depression is a complex illness that is affected by a variety of different things, which makes it very difficult to determine exactly what factors affect it.
• It may take a very long time for vitamin D to improve the symptoms of depression, if it does at all.
• People who suffer from depression are more likely to spend significant amounts of time inside the house, which could explain why their levels of vitamin D are lower.
• Researchers suggest that vitamin D supplementation is likely to only improve the symptoms of depression in people who actually have a vitamin D deficiency.
Resources and References:
Vitamin D and Depression – Role of vitamin D in depression. (Vitamin D Council)
Low Vitamin D Levels Linked to Depression in Young Women – Effects of vitamin D deficiency on depression in women. (Massachusetts General Hospital)
Vitamin D Levels Predict Depression – Link between vitamin D deficiency and depression. (Medscape)
Low Vitamin D Levels and Depression Linked in Young Women, New OSU Study Shows – Relationship between vitamin D deficiency and depression in women. (Oregon State University)