TF and major depressive disorder: Higher vitamin D levels have been associated with various further favorable health effects, which we did not consider in this analysis, such as decreased systolic blood pressure [27], immune modulation [28], improved cognitive function in older adults with Alzheimer's disease [29], lower risk of acute respiratory infections, dementia, cognitive decline, and depression mainly in elderly [30], increased muscle strength [31], and positive effects on transferrin saturation and iron status [32].