Table 1.

The patient, intervention/exposure, comparator, outcome, and study design (PICOS) criteria.

PICOS Criterion	Inclusion	Exclusion
Population	Adult patients with depression diagnosed	Pregnant women, patients with any concurrent physical disease or disability, patients with concurrent eating disorders, patients with concurrent intellectual disabilities
Intervention/exposure	Vitamin D oral supplementation of known dose	Multiple nutrients supplementation
Comparison	Compared with control group	No comparison with control group without vitamin D supplementation
Outcome	Depression monitored	No valid mental health outcome measure applied
Study design	Randomized Controlled Trials (RCTs) published as articles in peer-reviewed journals	Studies not published in English, animal model studies