The study used data from Finland’s national Health 2000 Survey, amounting to 5371 individuals aged 30–79 years of whom 354 were diagnosed with depressive disorder and 222 with anxiety disorder.
Individuals with higher serum 25(OH)D concentrations showed a reduced risk of depression, according to the study published in the British Journal of Nutrition. However, the same could not be said for anxiety.
“These results support the hypothesis that higher serum 25(OH)D concentrations protect against depression even after adjustment for a large number of socio-demographic, lifestyle and metabolic factors,” wrote the researchers from the National Institute for Health and Welfare in Helsinki.
The population attributable fraction (PAF) - the proportion of cases that can be attributed to one or more risk factors – was 19% for depression when serum vitamin D concentrations were at least 50 nanomoles/litre (nmol/l). This means raising serum levels above 50 nmol/l could have avoided about 19% of the depression cases in the study, the researchers said.
The key findings
The results found a weaker association amongst the participants over 59 years – although they said this could be explained by a greater prevalence of both depression and low vitamin D in the younger participants.
Meanwhile, the link between higher vitamin D and a lower depression risk was seen in particular for those who were divorced, had an unhealthier diet or lifestyle or had a metabolic syndrome.
If such a causal relationship was established, this could mean vitamin D’s protection against depression was especially strong for individuals with poor socio-economic status, lifestyle choices and metabolic health.
They also found individuals free from chronic diseases or anxiety disorder demonstrated a stronger association than those suffering from these conditions.
Who has the highest?
Those with the highest vitamin D levels were more likely to be older, married or cohabiting, more educated and without economic problems compared to those with lower levels.
This group had a healthier lifestyle since they were leaner, more active in their leisure time, smoked less and consumed less alcohol. They ate better and got more vitamin D from their diet and supplements, according to the food intakes recorded by the participants.
This higher level group also had better metabolic health in terms of blood pressure, triglyceride, glucose and cholesterol levels. They also perceived their health to be better.
Public saving potential
The researchers said the findings could have big public spending implications – with Finland currently spending about €1bn on depression per year.
Epidemiological evidence of this link had previously been scarce, they said, and large-scale prospective studies were now needed to confirm the relationship.
Source: British Journal of Nutrition
Published online ahead of print, doi:10.1017/S0007114515000689
“Higher serum 25-hydroxyvitamin D concentrations are related to a reduced risk of depression”
Authors: T. Jaaskelainen, P. Knekt, J. Suvisaari, S. Mannisto, T. Partonen, K. Saaksjarvi, N. E. Kaartinen, N. Kanerva and O. Lindfors