I understand this is not intended to be of double blind official study it's just someone's own attempts to quantify the impact on stress levels, but it is impor

I understand this is not intended to be of double blind official study it's just someone's own attempts to quantify the impact on stress levels, but it is important to note that vitamin d is not a neutral substance in the body. Also the amount of vitamin d taken is above the recommended daily allowance. Although the recommended daily allowance is quite small compared to the amount of vitamin d your body would produce just spending some time in the sun. Specifically there is enough research to link vitamin d deficiencies with stress and anxiety. So supplementing vitamin d, even in such small quantities, can skew the results. Since this occurred over a period of 16 months Sun exposure which results in your body producing vitamin d is changing up the "placebo control" variable. This is the difficult problem when trying to study the effect of any supplement. Many times they're effects are quite subtle and it's difficult to control for all of the other variables that may produce similar outcomes. Without accounting for all of the other variables that are part of it it's difficult to see if there is a correlation to the supplements or potentially to something else.