Nicole Bubes

Date of Award


Degree Type

Selective Evidence-Based Medicine Review

Degree Name

Master of Science in Health Sciences - Physician Assistant


Physician Assistant Studies

Department Chair

John Cavenagh, MBA, PhD, PA-C


Objective: The objective of this selective EBM review is to determine whether or not L-theanine, an amino acid analogue found in green tea leaves, is an effective treatment for reducing anxiety in patients ages 18-25.

Study design: Review of two double-blind, randomized controlled studies and one single-blind, randomized controlled study published in 2007, 2012 and 2013 respectively.

Data sources: PubMed

Outcome(s) measured: Each study measured L-theanine’s ability to reduce acute anxiety with a series of self-report measures assessing acute anxiety and stress, including the Profile of Mood States (POMS), the visual analogue scales (VAS), State-Trait Anxiety Inventory (STAI) and achievement emotion measurement.

Results: Kimura and colleagues found that state-trait anxiety inventory scores were significantly lower in the L-theanine group compared to placebo, Yoto and colleagues found that L-theanine significantly decreased tension-anxiety scores compared to placebo and Unno and colleagues found that scores of subjective stress were significantly lower in the L-theanine group compared to placebo.

Conclusion: Each reviewed study provides convincing and statistically significant evidence that that L-theanine has the potential to reduce symptoms of anxiety. However, there were inconsistencies. All three studies used VAS as a self-report measure, but only Unno and colleagues found VAS scores to be significantly reduced. Similarly, STAI scores were only significantly lowered in the study by Kimura and colleagues. Despite these discrepancies, the studies demonstrate a likely benefit of L-theanine reducing anxiety-related symptoms.