Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial

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#adult #anxiety #body-mass-index #cognition #cross-over-studies

Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial

Hidese et al., 2019 | Nutrients | Rct

Citation

Hidese Shinsuke, Ogawa Shintaro, ... Kunugi Hiroshi. Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial. Nutrients. 2019-Oct-03;11(10). doi:10.3390/nu11102362

Abstract

This randomized, placebo-controlled, crossover, and double-blind trial aimed to examine the possible effects of four weeks L-theanine administration on stress-related symptoms and cognitive functions in healthy adults. Participants were 30 individuals (nine men and 21 women; age: 48.3 ± 11.9 years) who had no major psychiatric illness. L-theanine (200 mg/day) or placebo tablets were randomly and blindly assigned for four-week administration. For stress-related symptoms, Self-rating Depression Scale, State-Trait Anxiety Inventory-trait, and Pittsburgh Sleep Quality Index (PSQI) scores decreased after L-theanine administration (p = 0.019, 0.006, and 0.013, respectively). The PSQI subscale scores for sleep latency, sleep disturbance, and use of sleep medication reduced after L-theanine administration, compared to the placebo administration (all p < 0.05). For cognitive functions, verbal fluency and executive function scores improved after L-theanine administration (p = 0.001 and 0.031, respectively). Stratified analyses revealed that scores for verbal fluency (p = 0.002), especially letter fluency (p = 0.002), increased after L-theanine administration, compared to the placebo administration, in individuals who were sub-grouped into the lower half by the median split based on the mean pretreatment scores. Our findings suggest that L-theanine has the potential to promote mental health in the general population with stress-related ailments and cognitive impairments.

Key Findings

Our findings suggest that L-theanine has the potential to promote mental health in the general population with stress-related ailments and cognitive impairments.

Outcomes Measured

  • sleep quality
  • PSQI (Pittsburgh Sleep Quality Index)
  • anxiety
  • depression

Population

Field Value
Population healthy adults
Sample Size 30
Age Range See abstract
Condition sleep

MeSH Terms

  • Adult
  • Anxiety
  • Body Mass Index
  • Cognition
  • Cross-Over Studies
  • Depression
  • Double-Blind Method
  • Female
  • Glutamates
  • Humans
  • Male
  • Middle Aged
  • Placebos
  • Sleep Wake Disorders
  • Stress, Psychological

Evidence Classification

  • Level: Rct
  • Publication Types: Journal Article, Randomized Controlled Trial
  • Vertical: l-theanine-anxiety

Provenance

Source extracted via PubMed E-utilities API on 2026-04-09