A LACK of vitamin D has long been linked to depression, but researchers believe it may contribute to psychiatric conditions such as personality disorders and post-traumatic stress disorder.

A study of more than 50 patients at a private psychiatric clinic in Geelong found that almost 60 per cent were suffering a severe vitamin D deficiency and 11 per cent were moderately deficient, prompting researchers to question whether vitamin D supplements could reduce mental illness across the board.

Vitamin D, which is mainly synthesised from ultraviolet light, regulates calcium and phosphorous levels in the blood and promotes bone mineralisation and bone growth.

Most people require only about 15 minutes of sunlight a day on their arms and face to produce an adequate amount of vitamin D. But sunscreen with a sun protection factor of eight blocks the body's ability to absorb the ultraviolet light.

An increasingly indoors lifestyle and a heightened awareness of the sun-exposure risks have also been blamed for people avoiding sunlight.

The study, published in the Australian And New Zealand Journal Of Psychiatry, found the 53 patients, who suffered bipolar disorder, depression, post-traumatic stress disorder or schizo-affective disorder, had vitamin D serum levels about 29 per cent lower than a group with no mental illness.

Kate Benson