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Head-to-head evidence comparison — which supplement is right for you?
L-Theanine and St. John's Wort are closely matched across evidence, studies, and safety.
Verdict
Likely helps
3 of 4 studies with measurable effects showed benefit.
Top outcomes
Verdict
Mixed evidence
4 of 9 studies with measurable effects showed benefit.
Top outcomes
100-200mg
Morning with coffee for focus, Evening for relaxation, As needed for stress
Suntheanine® capsules or powder
300mg 3x daily (900mg total)
With meals, Divided into 2-3 doses
Standardized extract (0.3% hypericin)
30-60 minutes
30-60 minutes
30-60 minutes
Varies
4-6 weeks
4-8 weeks
During use
First 1-2 weeks
The effects of L-theanine consumption on sleep outcomes: A systematic review and meta-analysis
Sleep medicine reviews (2025) · Meta analysis · n=897
The findings indicate the potential use of L-theanine in the management of sleep disturbances; however, the lack of studies on "pure" L-theanine warrants further investigation.
Efficiency of Different Supplements in Alleviating Symptoms of ADHD with or Without the Use of Stimulants: A Systematic Review
Nutrients (2025) · Systematic review
The evidence revealed the potential use of supplements as complementary ADHD treatments under clinical guidance.
Analysis of the Effects of Known Sleep-Support Supplements in Relation to Life Habits, Sleep Conditions, and Sleep Problems
Nutrients (2023) · Rct · n=160
All the tested supplements were found to ameliorate sleep problems significantly (Analysis 1).
St John's wort for major depression
Cochrane Database of Systematic Reviews (2008) · Meta analysis · n=5489
As effective as standard antidepressants for mild-moderate depression
Efficacy of Pharmacological Interventions in Milder Depression: A Systematic Review and Meta-Analysis
Neuropsychopharmacology reports (2025) · Meta analysis · n=1049
A meta-analysis found no significant difference in response rates between the two treatments (risk ratio [RR] = 0.96, 95% CI: 0.78-1.18) or dropout rates (RR = 1.08, 95% CI: 0.62-1.88).
Systematic Review and Network Meta-Analysis of the Effects of Plant Extracts on Cognitive Function and Quality of Life in Stroke Patients
Phytotherapy research : PTR (2025) · Meta analysis
John's Wort extract (SUCRA 71.2%) was the most effective in reducing NIHSS scores, Berberine (SUCRA 84.1%) was most effective in reducing mRS scores, and St.
Meta-analysis (n=897) and multiple RCTs support sleep benefits. Studies often used L-theanine in combination with other compounds, limiting pure L-theanine effect attribution. Effects include reduced sleep onset latency and improved subjective sleep quality.
Based on multiple meta-analyses (n>5000) showing efficacy comparable to SSRIs for mild-moderate depression. Effect plateau around 900-1200mg. Not effective for severe depression. Requires standardized extract (0.3% hypericin).
AI-estimated from published studies. Interpret as directional guidance.
Both L-Theanine and St. John's Wort are closely matched — the best choice depends on your specific health goals.
For support mood, St. John's Wort has a higher relevance score (92 vs 65).
No known interactions between L-Theanine and St. John's Wort have been documented in our database. However, always consult a healthcare provider before combining supplements.