Melatonin vs L-Theanine for cognition: which has better evidence?
Melatonin has the stronger evidence for cognition (Melatonin Grade B vs L-Theanine Grade C). For cognition, Melatonin has the stronger evidence grade.
Platform evidence comparison
These existing platform assessments are separate from the source-reported findings below. They do not represent a direct trial comparing these treatments.
| Melatonin | L-Theanine | |
|---|---|---|
| Grade | grade B | grade C |
| Certainty | moderate | moderate |
| Effect | Meta-analysis of RCTs in older adults with cognitive impairment: melatonin produced a modest improvement in cognition (MMSE +1.8 points) and total sleep time (+12.4 minutes), with a small reduction in neuropsychiatric symptoms. The authors conclude effects approach — but fall short of — definitive clinical efficacy, with substantial heterogeneity between trials. | improves attention and cuts down distraction, especially paired with caffeine |
| Studied dose | varies; taken at bedtime | 100–200 mg |
| Population | older adults with cognitive impairment | adults |
| Safety | 1 modeled interaction(s) | 0 modeled interaction(s) |
Grade B / moderate: probably helps, and new studies are unlikely to reverse this — but could shrink the effect size.
Direct comparison evidence
There are no direct RCTs in our corpus comparing Melatonin and L-Theanine head-to-head for cognition. What we present above is an indirect comparison: each side's own trials, contrasted. This is standard practice for supplement comparisons — dose, population, and outcome-instrument differences between the two evidence bases add uncertainty on top of each side's own grade.
Can you take both?
No modeled interaction between Melatonin and L-Theanine in our corpus. Absence of a recorded interaction is not proof of additive benefit — combined-effect trials are usually absent for supplement pairs, so treat "stack" claims skeptically.
Decision guidance
- If certainty matters most — choose whichever side carries the higher certainty rating at a similar grade.
- If you're on medications — check each side's interaction pages before deciding; safety differences dominate small evidence-grade gaps.
- If your population is under-studied — the smaller-effect side with better population evidence often wins over the higher-grade side studied in a different demographic.
- If cost matters — form and dose page differences (Melatonin vs L-Theanine) can invert the practical winner.
Grade history
No grade changes yet. Initial grade assigned; re-reviewed on every 12 months (Grade A/B) — next review by . Methodology v1.
Re-review cadence: every 12 months (Grade A/B) · next scheduled by · methodology v1.
Frequently asked
Which has stronger evidence: Melatonin or L-Theanine for cognition?
Melatonin carries Grade B at moderate certainty; L-Theanine carries Grade C at moderate. The stronger evidence points to Melatonin, subject to the caveat that direct head-to-head trials are usually absent for supplement pairings.
Can I take Melatonin and L-Theanine together?
No modeled interaction between Melatonin and L-Theanine; combining is not documented to be problematic, but combined-effect trials are also absent, so treat additive benefit claims skeptically.
Have Melatonin and L-Theanine been compared head-to-head?
Direct RCTs comparing the two for cognition are uncommon. This page contrasts each side's own trial evidence — that is an indirect comparison, which introduces confounds from population and dose differences. See the direct-comparison block above.
What decides between Melatonin and L-Theanine for me?
Read the decision guidance below — the split usually comes down to population fit, interaction risk with your other medications, and how much certainty you want behind the recommendation.
Related
Cite this page
Citation is encouraged. The proposed reuse license is CC-BY-4.0; status: pending-governance-ratification.
Plain-text citation
Substrate. Melatonin vs L-Theanine for cognition. https://evidencebased.info/compare/melatonin-vs-theanine-for-cognition. Updated 2026-07-14.
BibTeX
@misc{substrate_theanineforcognition,
author = {Substrate editorial},
title = {Melatonin vs L-Theanine for cognition},
year = {2026},
url = {https://evidencebased.info/compare/melatonin-vs-theanine-for-cognition},
note = {evidencebased.info}
}