The efficacy of saffron in the treatment of mild to moderate depression: A meta-analysis  

A 2019 meta-analysis examined the results of 11 randomized control trials with 531 pooled subjects published from 2004-2018, to assess whether supplementation with whole saffron extracts was effective in the management of mild to moderate depression. These trials did in fact indicate significant efficacy over placebo, further the results were comparable to commonly prescribed antidepressant drug and were well tolerated. 

References:

Tóth B, Hegyi P, Lantos T, et al. The Efficacy of Saffron in the Treatment of Mild to Moderate Depression: A Meta-analysis. Planta Med. 2019;85(1):24-31. doi:10.1055/a-0660-9565  https://pubmed.ncbi.nlm.nih.gov/30036891/