Improvement after a supplement is not the same as a comparative result
Start with the comparison. A before-and-after change alone cannot isolate the contribution of an ingredient.
L-Theanine
Selected research topic
Sleep
Findings differ across measurements or study conditions. The results below keep them separate.
Findings from a combination study cannot be attributed to this ingredient alone.
Some findings concern patients or people with a deficiency.
- Publications for this topic
- 15
- Human comparison publications
- 3
- Publications needing review
- 10
Findings in the studies
Insomnia symptoms
About this measure
Insomnia Severity Index (ISI)
- No clear difference from the comparison group was found.
What the comparison group used was not confirmed.
Single ingredientMeasurement and study conditions
- Study type
- Randomized controlled trial: subjects were randomly assigned to groups for comparison.
- Study population
- Human participants · Participant characteristics were not confirmed.
- Ingredients tested
- Single ingredient
- How results were compared
- Results were compared between groups.
- Measurement time
- Not confirmed.
Sleep quality
About this measure
Pittsburgh Sleep Quality Index (PSQI) · mean score
- No clear difference from the comparison group was found.
Several ingredients were tested together, so this ingredient’s individual effect is unknown.
Patient group · Combination study · 6 weeksMeasurement and study conditions
- Study type
- Randomized controlled trial: subjects were randomly assigned to groups for comparison.
- Study population
- Human participants · Patient group
- Ingredients tested
- Ingredient combination
- How results were compared
- Results were compared between groups. · Study comparison: four-ingredient formulation versus placebo
- Additional measurement information
- Primary outcome
- Measurement time
- 6 weeks
sleep efficiency
- A better result than the comparison group was reported.
What the comparison group used was not confirmed.
Patient group · Single ingredientMeasurement and study conditions
- Study type
- Randomized controlled trial: subjects were randomly assigned to groups for comparison.
- Study population
- Human participants · Patient group
- Ingredients tested
- Single ingredient
- How results were compared
- Results were compared between groups.
- Measurement time
- Not confirmed.
Sleep quality
About this measure
Pittsburgh Sleep Quality Index (PSQI) · total score
Other human research, including observational studies and reviews
- A change was reported before and after use. Its cause cannot be isolated.
Several ingredients were tested together, so this ingredient’s individual effect is unknown.
Patient group · Combination study · 4 weeksMeasurement and study conditions
- Study type
- Clinical trial
- Study population
- Human participants · Patient group
- Ingredients tested
- Ingredient combination
- How results were compared
- Changes within the same group were compared. · Study comparison: within-group pre/post combination intake
- Additional measurement information
- Primary outcome
- Measurement time
- 4 weeks
Other measured outcomes (1)
sleep-onset latency
Research with unclear study subject or type
- A change was reported, but the comparison could not be confirmed.Varied across included studies
Measurement and study conditions
- Study type
- Systematic review
- Study population
- Recorded population category: Patient group. Whether the research involved humans needs confirmation.
- Ingredients tested
- Unknown intervention
- How results were compared
- Study comparison: Mixed ADHD treatments including L-theanine; no common comparator
- Additional measurement information
- Secondary outcome
- Measurement time
- Varied across included studies
This result is held for interpretation. That does not mean research found no effect.
Outcome groups needing additional review (10)
- morning sleepiness · Distinct papers needing additional review: 1Direction unclear: 1
- overall subjective sleep quality score · Distinct papers needing additional review: 1Evidence criteria check: 1
- sleep duration · Distinct papers needing additional review: 2Evidence criteria check: 2
- sleep latency · Distinct papers needing additional review: 1Evidence criteria check: 1
- sleep onset latency · Distinct papers needing additional review: 2Direction unclear: 1 · Evidence criteria check: 1
- sleep problems · Distinct papers needing additional review: 1Direction unclear: 1
- Sleep quality · Distinct papers needing additional review: 1Direction unclear: 1
- subjective daytime dysfunction · Distinct papers needing additional review: 1Evidence criteria check: 1
- subjective sleep onset latency · Distinct papers needing additional review: 1Evidence criteria check: 1
- total sleep time · Distinct papers needing additional review: 1Direction unclear: 1
One paper can appear under multiple measured outcomes or review reasons, so these counts should not be added together.
Representative outcome and study details
Partial research summary
Human studies reported between-group improvement in sleep efficiency.
These conditions come from related studies and may not describe a single paper.
single- and combination-ingredient studies · Individual ingredient effects cannot be separated · Human studies · Includes patient groups · between-group comparison · comparator not confirmed
2 publications linked to this result (1 awaiting review included)
- Study conditions differ; results are shown descriptively and are not pooled.
- Combination, formula, or class studies do not isolate this ingredient or establish synergy.
- Some publications have not cleared source or interpretation review.
- Some papers could not be reviewed, so this summary covers only findings that could be confirmed.
Data coverage and detailed study classifications
Paper counts are separated by research topic below. One paper may contribute to multiple findings.
Analysis status: Public-ready
Ingredient analysis date:
How the grade was determined: C
The 9.4 evidence score includes 3 independent human studies and 3 clinical studies in the representative benefit area. The C tier remains conservative because of limited repetition across independent human clinical studies.
The grade is based mainly on the research area with the most evidence. It does not mean the same result was found in other areas.
Papers linked to this ingredient overall: 97
Papers linked to this topic 15 · distinct papers 15 · papers with a confirmed human comparison 3 · papers needing additional review 10
A publication may appear in more than one count. These numbers should not be added. Ingredient-wide papers, topic-linked papers, and sources in outcome groups use different scopes. Adding source counts may count the same paper more than once.
- Insomnia symptoms (Insomnia Severity Index (ISI)): Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 1
- Sleep quality (Pittsburgh Sleep Quality Index (PSQI) · mean score): Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 1
- morning sleepiness: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- overall subjective sleep quality score: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- sleep duration: Sources represented in this measurement group: 2 · Distinct papers with human comparisons for this outcome: 0
- sleep efficiency: Sources represented in this measurement group: 2 · Distinct papers with human comparisons for this outcome: 1
- sleep latency: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- sleep onset latency: Sources represented in this measurement group: 2 · Distinct papers with human comparisons for this outcome: 0
- sleep problems: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- Sleep quality: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- sleep-onset latency: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- subjective daytime dysfunction: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- subjective sleep onset latency: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- Sleep quality (Pittsburgh Sleep Quality Index (PSQI) · total score): Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
- total sleep time: Sources represented in this measurement group: 1 · Distinct papers with human comparisons for this outcome: 0
What the research found
Insomnia Severity Index
No clear difference in this measurement was found between the compared groups.
Controlled study in people · Single ingredient · Unspecified population
Between-group comparison
Analysis coverage and paper counts
1 paper · 1 measured outcome
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
Mean PSQI
No clear difference in this measurement was found between the compared groups.
Controlled study in people · Ingredient combination · Patient group
Several ingredients were used together. This does not establish the effect of this ingredient alone or synergy.
Between-group comparison
Analysis coverage and paper counts
1 paper · 1 measured outcome
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
sleep efficiency
The study reported improvement in this measurement.
Controlled study in people · Single ingredient · Patient group
Between-group comparison
Analysis coverage and paper counts
1 paper · 1 measured outcome
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
total PSQI score
A change was reported before and after use. Its cause cannot be isolated.
Other evidence · Ingredient combination · Patient group
Several ingredients were used together. This does not establish the effect of this ingredient alone or synergy.
Within-group comparison
Analysis coverage and paper counts
1 paper · 1 measured outcome
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
sleep-onset latency
A change was reported, but the comparison could not be confirmed.
Review · Unknown intervention · Patient group
Analysis coverage and paper counts
1 paper · 1 measured outcome
Review overlap with primary papers is unknown; counts stay separate.
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
morning sleepiness
The study needs further checking before its result can be interpreted.
Controlled study in people · Ingredient combination · General population
Several ingredients were used together. This does not establish the effect of this ingredient alone or synergy.
The comparison could not be confirmed.
Analysis coverage and paper counts
1 paper · 1 measured outcome
1 papers held from direction counts
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
overall subjective sleep quality score
The study needs further checking before its result can be interpreted.
Meta-analysis · Unknown intervention · General population
The comparison could not be confirmed.
Analysis coverage and paper counts
1 paper · 1 measured outcome
1 papers held from direction counts
Review overlap with primary papers is unknown; counts stay separate.
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
sleep duration
The study needs further checking before its result can be interpreted.
Animal study · indirect · Ingredient combination · Unspecified population
This finding comes from animal or cell research. It does not establish the same effect in people.
Several ingredients were used together. This does not establish the effect of this ingredient alone or synergy.
Between-group comparison
Analysis coverage and paper counts
1 paper · 1 measured outcome
1 papers held from direction counts
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
sleep duration
The study needs further checking before its result can be interpreted.
Animal study · indirect · Separable contribution · General population
This finding comes from animal or cell research. It does not establish the same effect in people.
The comparison could not be confirmed.
Analysis coverage and paper counts
1 paper · 1 measured outcome
1 papers held from direction counts
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
sleep efficiency
The study needs further checking before its result can be interpreted.
Controlled study in people · Ingredient combination · General population
Several ingredients were used together. This does not establish the effect of this ingredient alone or synergy.
The comparison could not be confirmed.
Analysis coverage and paper counts
1 paper · 1 measured outcome
1 papers held from direction counts
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
sleep latency
The study needs further checking before its result can be interpreted.
Controlled study in people · Single ingredient · General population
Between-group comparison
Analysis coverage and paper counts
1 paper · 1 measured outcome
1 papers held from direction counts
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
sleep onset latency
The study needs further checking before its result can be interpreted.
Animal study · indirect · Ingredient combination · General population
This finding comes from animal or cell research. It does not establish the same effect in people.
Several ingredients were used together. This does not establish the effect of this ingredient alone or synergy.
Between-group comparison
Analysis coverage and paper counts
1 paper · 1 measured outcome
1 papers held from direction counts
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
sleep onset latency
The study needs further checking before its result can be interpreted.
Controlled study in people · Ingredient combination · General population
Several ingredients were used together. This does not establish the effect of this ingredient alone or synergy.
The comparison could not be confirmed.
Analysis coverage and paper counts
1 paper · 1 measured outcome
1 papers held from direction counts
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
sleep problems
The study needs further checking before its result can be interpreted.
Controlled study in people · Single ingredient · General population
The comparison could not be confirmed.
Analysis coverage and paper counts
1 paper · 1 measured outcome
1 papers held from direction counts
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
Sleep quality
The study needs further checking before its result can be interpreted.
Other evidence · Single ingredient · Patient group
The comparison could not be confirmed.
Analysis coverage and paper counts
1 paper · 1 measured outcome
1 papers held from direction counts
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
subjective daytime dysfunction
The study needs further checking before its result can be interpreted.
Meta-analysis · Unknown intervention · General population
The comparison could not be confirmed.
Analysis coverage and paper counts
1 paper · 1 measured outcome
1 papers held from direction counts
Review overlap with primary papers is unknown; counts stay separate.
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
subjective sleep onset latency
The study needs further checking before its result can be interpreted.
Meta-analysis · Unknown intervention · General population
The comparison could not be confirmed.
Analysis coverage and paper counts
1 paper · 1 measured outcome
1 papers held from direction counts
Review overlap with primary papers is unknown; counts stay separate.
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
total sleep time
The study needs further checking before its result can be interpreted.
Controlled study in people · Ingredient combination · General population
Several ingredients were used together. This does not establish the effect of this ingredient alone or synergy.
The comparison could not be confirmed.
Analysis coverage and paper counts
1 paper · 1 measured outcome
1 papers held from direction counts
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
Unspecified measured outcome
The study needs further checking before its result can be interpreted.
Controlled study in people · Ingredient combination · Unspecified population
Several ingredients were used together. This does not establish the effect of this ingredient alone or synergy.
Between-group comparison
Analysis coverage and paper counts
1 paper · 1 measured outcome
1 papers held from direction counts
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
Unspecified measured outcome
The study needs further checking before its result can be interpreted.
Other evidence · Unknown intervention · Unspecified population
The comparison could not be confirmed.
Analysis coverage and paper counts
1 paper · 1 measured outcome
Direction counts are distinct papers within each row. Outcome contributions count endpoint results, so one paper may contribute more than once.
How to read research findings
How should I read research findings?
Research guidesNo clear difference and an uninterpretable result are different
A reported null comparison contains a result. An abstract without an interpretable comparison leaves a question unresolved.
Paper counts and study counts are different
Count original research separately from research that reanalyzes it. Publication volume is neither replication nor a quality rating.
Side effects and combination findings
Findings from this ingredient alone are shown separately from those involving another supplement or medication.
No combination cautions are available to show in the current data. This does not guarantee safety.
Review 1 combination findings and 0 findings that outperformed an ingredient alone.
Reported improvements with combinations
Combination findings are grouped by how the study compared them. This is not a recommendation to combine ingredients.
Combinations with reported improvement
The combination showed improvement, but each ingredient's contribution is unclear.
CaffeineL-theanine combined with caffeine significantly reduced caffeine-induced tachycardia (17% vs 92%) and state anxiety compared to caffeine alone.