Combined treatment with two water extracts of Eleutherococcus senticosus leaf and rhizome of drynaria fortunei enhances cognitive function: A placebo-controlled, randomized, double-blind study in healthy adults 

In 2020 researchers performed a placebo-controlled, randomized, double-blind study to evaluate cognitive enhancement and anti-stress effects by the intake of a combined extract in healthy volunteers. The intake period was 12 weeks. The combined treatment of ES and DR extracts significantly increased the figure recall subscore of RBANS (p = 0.045) in an intergroup comparison.  No adverse effects were observed. The combined treatment of ES and DR extracts appear to safely enhance a part of cognitive function in healthy adults. 

References:

Tohda C, Matsui M, Inada Y, et al. Combined Treatment with Two Water Extracts of Eleutherococcus senticosus Leaf and Rhizome of Drynaria fortunei Enhances Cognitive Function: A Placebo-Controlled, Randomized, Double-Blind Study in Healthy Adults. Nutrients. 2020;12(2):303. Published 2020 Jan 23. doi:10.3390/nu12020303 https://pubmed.ncbi.nlm.nih.gov/31979283/