London: Lower levels of vitamin D are likely to trigger a gloomy outlook among older men and women, according to a new study.

About 13 percent of older individuals have symptoms of depression, caused by negligible presence of vitamin D, which might also spur other psychiatric illnesses, researchers say.

"Underlying causes of vitamin D deficiency such as less exposure to sun, different housing or clothing habits and decreased vitamin intake may be secondary to depression, but depression may also be the consequence of poor vitamin D status," the study's authors write.

"Moreover, poor vitamin D status causes an increase in serum parathyroid hormone levels." Overactive parathyroid glands are frequently accompanied by symptoms of depression that disappear after treatment.

Witte J.G. Hoogendijk and colleagues at VU University Medical Centre, the Netherlands, measured blood levels of vitamin D and parathyroid hormone and among 1,282 depressed people aged between 65 and 95.

Of those individuals, 26 were diagnosed with major depressive disorder, 169 had minor depression and 1,087 were not depressed.

Blood vitamin D levels were 14 percent lower in individuals with major and minor depression, compared to normal participants.

In addition, thyroid levels were an average of five percent higher in those with minor depression and 33 percent higher in those with major depressive disorder than in those who were not depressed.

The report appears in the May issue of Archives of General Psychiatry. IANS