In the study, doctors measured vitamin D levels in 2,752 10-year-olds and followed up for four years. Children who began the study with higher levels of vitamin D were more likely to show a decline in depressive symptoms during the follow-up period, and were 10 percent less likely to have depressive symptoms at the end of four years.
Talking about their findings, doctors said that because depression can affect so many children and adolescents, and because it is so easy to increase vitamin D levels, new research should include larger studies to see if it is possible to prevent depressive symptoms in young people. Doctors also said that it was not vitamin D2, but vitamin D3 that provides the benefit in reducing symptoms of depression.
Doctors believe the optimal range for vitamin D blood levels is 20 to 60 nanograms per milliliter of blood, or 50 to 150 nanomoles per liter.