This could in turn put them at risk of serious health problems, including osteoporosis, muscle pain, or weakness.
Researchers are calling for all psychiatric inpatients to be routinely screened for vitamin D deficiency.
The small-scale study involved 17 male patients in a low security psychiatric service and was carried out by researchers from St Bernard’s Hospital in Middlesex.
Blood tests revealed that none of the patients had enough vitamin D. Two had a borderline deficiency and the other 15 deficiency.
Seven of the patients had such low vitamin D levels that tests were unable to produce an accurate reading.
Of the 17 inpatients, 10 were African or African-Caribbean, two were of mixed ethnicity, one was Vietnamese.
Researchers said that psychiatric inpatients may be vulnerable to vitamin D deficiency because of a lack of exposure to sunlight, poor diet and physical health, the use of certain drugs and an over-representation of ethnic groups know to be at greater risk.
They recommend that mental health inpatients receive their recommended daily allowance of vitamins and minerals and adequate exposure to sunlight.
Psychiatric Bulletin (2008) 32:390-393