The acute effects of Zensera™ (Melissa officinalis L.) extract on mood and cognitive performance during cognitive overload: a randomised placebo-controlled, double blind study in healthy young adults with moderate subjective stress

Background: Chronic cognitive overload strains working memory and activates the body’s stress response via the hypothalamic–pituitary–adrenocortical axis, potentially causing stress-related health issues. Over-the-counter herbals, including lemon balm extract, are gaining popularity for stress management, possibly due to their lack of side effects. Objectives: To examine whether Zensera™, a lemon balm extract, produced mood and cognitive improvements throughout the day, 106 young healthy adults, with moderate stress complaints, were tested to compare the effects of 300mg Zensera™ to a matched placebo during periods of cognitive overload. Design: An acute, parallel groups, randomised, double-blind, placebo-controlled design was implemented with cognitive function, mood, heart rate and blood pressure measured at baseline and at 1, 3 and 5h post-treatment. Methods: Overall subjective calmness (primary aim) and fatigue (secondary) were captured at the beginning and end of the test day. Other transient mood measures were captured throughout the day, before and after high cognitive demand sessions. Results: For the primary outcome, no changes in overall calmness emerged. Zensera™ elicited improved performance on the hardest executive function trials at 5h, and multiple regression confirmed that increased performance on the hardest attention network tasks was predicted by increased calmness and contentment at 5h. Finally, Zensera™ helped restore feelings of transient calmness following the impact of cognitive demand, which was not seen for the placebo. Conclusion: Overall, these findings provide evidence for acute protective effects of Zensera™ in stressed adults, with benefits for challenging executive function tasks and enhanced calmness recovery following cognitive effort. Further research exploring the impact of Zensera™ for chronic stress is warranted.