Vitamin D has been shown to be crucial in the regulation of dopamine and its relationship to major depressive disorder.

A five-year pre-interventional study of 25 hydroxy vitamin D levels in patients with major depressive disorder found values ranging from 17 to 32 ng/mL.

COMT Val/Val genotype has been associated with a 20–40% more rapid breakdown of dopamine in the prefrontal cortex as compared to individuals with a Val/Met genotype.

This retrospective study gathered data concerning outcome measurements in patients who displayed a baseline 25-OH level < 30 mg/mL and initially treated with sublingual tablet form of 10,000 IU vitamin D3. These data were compared to post interventional depression outcome scores for patients switched to oral vitamin D3 drops at a dose of 10,000 IUs.

Scores on the MADRS 1–3 weeks following the vitamin D3 switch showed an improvement in mood with the lowering of scores on the MADRS.

Patients with a COMT genotype of Val/Val showed clinical improvement with a switch from oral D3 sublingual tablets to oral D3 drops. Further studies are needed to draw from conclusions. Pre- and post-25-OH vitamin D levels and other dopamine synthesis variables including serum ferritin would be useful as well as prospective double-blind placebo controlled trials. The future use of genotype-specific and supportive approaches deserves serious investigation.

The author has not supplied his/her declaration of competing interest.