When studying the relationship between vitamin D levels and cognition, researchers found that “the high vitamin d group had significantly more correct responses than the low vitamin d group”. 
A meta-analysis of 18 independent randomized controlled trials (total 57,311 participants) found that “Intake of ordinary doses of vitamin d supplements seems to be associated with decreases in total mortality rates”. 
An extensive 2007 study on 2,160 healthy women concluded that “higher vitamin D concentrations are associated with longer LTL, which underscores the potentially beneficial effects of this hormone of aging and age-related diseases”. 
A rodent study investigating the neuroprotective effects of vitamin D discovered it’s ability to mitigate inflammation, making it “a useful therapeutic option to alleviate the effects of aging on cognitive function”. 
Dr. Rhonda Patrick recently discovered that “Vitamin D hormone regulates serotonin synthesis”. Serotonin is the neurotransmitter responsible for mood regulation. 
A study examining the cognitive performance, mood, and physical performance of 80 older adults found that “vitamin D deficiency was associated with low mood and with impairment on two of four measures of cognitive performance”. 
- Vitamin D and executive function: a preliminary report.
- Vitamin D supplementation and total mortality: a meta-analysis of randomized controlled trials.
- Higher serum vitamin d concentrations are associated with longer leukocyte telomere length in women.
- Vitamin D mitigates age-related cognitive decline through the modulation of pro-inflammatory state and decrease in amyloid burden.
- Vitamin D hormone regulates serotonin synthesis. part 1; relevance for autism.
- Vitamin D deficiency is associated with low mood and worse cognitive performance in older adults.