Low blood levels of vitamin D and high blood levels of parathyroid hormone boost the risk of depression in seniors. Vitamin D levels influences mood as it plays a significant role in several neurological and hormonal processes. Previous studies have linked altered levels of vitamin D and parathyroid hormone (PTH) but this relationship has not been studied systematically. In order to determine the relationship between levels of vitamin D and risk of developing depression, researchers in Denmark looked at 1,282 men and women aged 65—95 years participating in a long-term study on aging. Depression was measured using self-reports and interviews, and levels of vitamin D and PTH were assessed. Potentially confounding factors (like age, sex, smoking status, body mass index, chronic conditions, etc) and explanatory factors (including season of data acquisition, level of urbanisation and physical activity) were taken into consideration. Nearly 40 per cent of the men and 57 per cent women in the study had low levels of vitamin D in their blood. Vitamin D levels were 14 per cent lower in 169 people suffering from minor depression, and 26 with major depressive disorder, as compared to levels in 1087 individuals who were not depressed. Also, blood levels of parathyroid hormone, which increase with vitamin D deficiency, were five per cent higher in people with minor depression and 33 per cent higher in those with major depression, in comparison to levels seen in seniors without depression. Moreover, depression severity was significantly associated with decreased serum vitamin D levels and increased serum PTH levels. The findings underline the association between vitamin D levels and depression; however, it still remains unclear whether low vitamin D levels and high blood levels of parathyroid are a cause or a consequence of depression. If vitamin D deficiency is a cause rather than a result of depression, supplementation with the vitamin and increased exposure to sunlight could help treat the mood disorder. But further long-term studies are needed to explore whether decreased vitamin D levels and increased parathyroid hormone levels precede depression or follow it.
Archives of General Psychiatry,
May 2008