Previous research has shown that low vitamin D levels may be associated with increased disease severity in psychotic disorders.
To explore which symptoms are affected by vitamin D status, a team from the Norwegian Centre for Mental Disorders Research recruited 358 patients and compared their vitamin D levels against measures of symptom severity.
The researchers found that low vitamin D levels were significantly associated with negative symptoms and depression. When they studied the performance of 225 patients alongside 159 healthy controls in cognitive function tests, vitamin D deficiency was also linked to impairments in processing speed and verbal fluency.
The team, who reported their findings at the International Early Psychosis Association Meeting in Milan in October 2016
, say the results show the need for large randomised trials to explore any potential benefit of vitamin D in psychotic disorders.
 Nerhus M, Berg AO & Melle I. Vitamin D in psychotic disorder — associations with symptomatology and cognition. Presented at International Early Psychosis Association Meeting; Milan, Italy; 20-22 October 2016. Abstract available from: http://www.iepaconference.org/page/?page=oral_sessions