L-theanine in the adjunctive treatment of generalized anxiety disorder: A double-blind, randomised, placebo-controlled trial.

2019-03
Journal of psychiatric research 110
- Jerome Sarris
- Gerard J Byrne
- Lachlan Cribb
- Georgina Oliver
- Jenifer Murphy
- Patricia Macdonald
- Sonia Nazareth
- Diana Karamacoska
- Samantha Galea
- Anika Short
- Carolyn Ee
- Yoann Birling
- Ranjit Menon
- Chee H Ng

PubMed: 30580081
DOI: 10.1016/j.jpsychires.2018.12.014

Study Design

Type: Randomized Controlled Trial (RCT)
Sample size: n = 46
Population: 46 participants with a DSM-5 diagnosis of Generalized Anxiety Disorder (GAD)
Methods: 10-week study (consisting of an 8-week double-blind placebo-controlled period, and 1-week pre-study and 2-week post-study single-blinded observational periods); participants received adjunctive L-theanine (450-900 mg) or matching placebo with their current stable antidepressant treatment
Blinding: Double-blind
Duration: 10 weeks
Funding: Unclear

Partial or non-response to antidepressants in Generalized Anxiety Disorder (GAD) is common in clinical settings, and adjunctive biological interventions may be required. Adjunctive herbal and nutraceutical treatments are a novel and promising treatment option. L-theanine is a non-protein amino acid derived most-commonly from tea (Camellia sinensis) leaves, which may be beneficial in the treatment of anxiety and sleep disturbance as suggested by preliminary evidence. We conducted a 10-week study (consisting of an 8-week double-blind placebo-controlled period, and 1-week pre-study and 2-week post-study single-blinded observational periods) involving 46 participants with a DSM-5 diagnosis of GAD. Participants received adjunctive L-theanine (450-900 mg) or matching placebo with their current stable antidepressant treatment, and were assessed on anxiety, sleep quality, and cognition outcomes. Results revealed that adjunctive L-theanine did not outperform placebo for anxiety reduction on the HAMA (p = 0.73) nor insomnia severity on the Insomnia Severity Index (ISI; p = 0.35). However, LT treated participants reported greater self-reported sleep satisfaction than placebo (ISI item 4; p = 0.015). Further, a separation in favour of L-theanine was noted on the ISI in those with non-clinical levels of insomnia symptoms (ISI ≤ 14; p = 0.007). No significant cognitive effects (trail making time and the modified emotional Stroop) were revealed. While this preliminary study did not support the efficacy of L-theanine in the treatment of anxiety symptoms in GAD, further studies to explore the application of L-theanine in sleep disturbance are warranted.

Research Insights

L-Theanine→Improved Emotional Stroop Performance
No significant cognitive effects (trail making time and the modified emotional Stroop) were revealed.
Effect
Neutral
Effect size
Small
Dose
450-900 mg
L-Theanine→Improved Insomnia Severity
a separation in favour of L-theanine was noted on the ISI in those with non-clinical levels of insomnia symptoms (ISI≤14; p=0.007)
Effect
Beneficial
Effect size
Small
Dose
450-900 mg/day
L-Theanine→Improved Sleep Satisfaction
LT treated participants reported greater self-reported sleep satisfaction than placebo (ISI item 4; p = 0.015)
Effect
Beneficial
Effect size
Small
Dose
450-900 mg
L-Theanine→Improved Trail Making Test Time
No significant cognitive effects (trail making time ...) were revealed
Effect
Neutral
Effect size
Small
Dose
450-900 mg/day
L-Theanine→Reduced Anxiety
Results revealed that adjunctive L-theanine did not outperform placebo for anxiety reduction on the HAMA (p = 0.73)
Effect
Neutral
Effect size
Small
Dose
450-900 mg
L-Theanine→Reduced Insomnia
a separation in favour of L-theanine was noted on the ISI in those with non-clinical levels of insomnia symptoms (ISI ≤ 14; p = 0.007)
Effect
Beneficial
Effect size
Small
Dose
450-900 mg
L-Theanine→Reduced Trail Making Test Completion Time
No significant cognitive effects (trail making time and the modified emotional Stroop) were revealed.
Effect
Neutral
Effect size
Small
Dose
450-900 mg