I was an RA at the RAND Corp who put together literature reviews for mental health interventions like this. The Vitamin D result is implausible. If true it would be the biggest breakthrough in the history of psychiatry.

This is the referenced meta-analysis: https://www.cambridge.org/core/journals/psychological-medici...

The largest N study (N=18,353; more than half of the entire 31 study sample) included is https://jamanetwork.com/journals/jama/fullarticle/2768978, which found: "Risk of depression or clinically relevant depressive symptoms was not significantly different between the vitamin D3 group...and the placebo group."

The highest dose study (100,000 IU/week) included is https://pubmed.ncbi.nlm.nih.gov/30532541/, which found: "...the treatment response or BDI scores did not differ significantly between groups."

The paper/supplementary materials doesn't include a simple table of the depression outcomes for the 31 included studies, which is a glaring omission.

I think someone just messed up here. Maybe missed a decimal place?

For a more realistic perspective, here's another careful meta-analysis of RCTs of Vitamin D for depression that found null result: https://www.sciencedirect.com/science/article/abs/pii/S08999... (granted, 2015). And another from 2025 that found a .36 effect size, which is plausible and still fantastic: https://www.frontiersin.org/journals/psychiatry/articles/10....

I don't mean to dissuade people from trying these given the low risk profile, just don't expect to go from a C to an A.