*Therapeutic use of vitamin D, *Well-being, *Medical quality control, *Psychotherapy patients, *Systematic reviews, *Health outcome assessment, *Mental health, *Medical screening, *Dietary supplements, *Comparative studies, *Psychosocial factors, *Hospital care, *Descriptive statistics, *Disease prevalence, *Vitamin D deficiency, *Mental illness, *Mental health services, *Disease complications

Objectives: Vitamin D deficiency is associated with worse physical and mental health outcomes. Low vitamin D levels are more common among people who experience mental health issues. This is particularly vital due to the outdoor restrictions which arose from the COVID-19 pandemic. This systematic review assessed vitamin D deficiency and insufficiency among psychiatric inpatients. Methods: A literature search was performed using the key words 'vitamin D', 'mental health', 'mental illness' and 'inpatient' and articles were selected by two independent reviewers. Eighteen studies were identified as eligible according to inclusion and exclusion criteria. Results: Vitamin D deficiency (29 − 96%) and insufficiency (20 − 63%) were common among psychiatric inpatients. Over half of the studies recommended or advised consideration of vitamin D level screening among psychiatric inpatients, while nine recommended consideration of vitamin D supplementation. Conclusions: Screening for vitamin D deficiency during psychiatric admission may be clinically indicated and improve patient wellbeing and outcomes. Low vitamin D levels are very common among people admitted to inpatient mental health services. Vitamin D level screening upon inpatient psychiatric admission is warranted to optimise general health outcomes. Vitamin D supplementation should be considered among inpatients with vitamin D deficiency or insufficiency. [ABSTRACT FROM AUTHOR]

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