This 2015 head to head study between Rhodiola rosea extract and the pharmaceutically prescribed antidepressant sertraline was observed in a phase II randomized placebo controlled clinical trial. Authors monitored the improvements by measuring the HAM-D scores over 12 weeks of treatment. The results for both treatment groups were clinically meaningful reductions over time in HAM-D scores though these results were not statistically significant compared to placebo.
Mao JJ, Xie SX, Zee J, Soeller I, Li QS, Rockwell K, Amsterdam JD. Rhodiola rosea versus sertraline for major depressive disorder: A randomized placebo-controlled trial. Phytomedicine. 2015 Mar 15;22(3):394-9. doi: 10.1016/j.phymed.2015.01.010. Epub 2015 Feb 23. PMID: 25837277; PMCID: PMC4385215.