Evidence map›Paper›PMID 17891480›Full record

Trial reportPsychopharmacology2008

Time for tea: mood, blood pressure and cognitive performance effects of caffeine and theanine administered alone and together.

Peter J Rogers, Jessica E Smith, Susan V Heatherley, C W Pleydell-Pearce

2 registry-linked trialsAbstract readComparative StudyRandomized Controlled Trial
PubMed Publisher
In one paragraph

Trial report in Psychopharmacology, 2008. The graph could read no effect estimate from its abstract, so it casts no vote on the map. It is linked to 2 registered trials, which are not on this map. Cited by 51 papers, 4 of them syntheses that pooled it.

0numbers the graph read from it
0cells of the map it votes in
51citing papers in PubMed, 4 pooled it
4.3field-weighted citation impact, top 5% of its field
1 · What the graph read from it

What it found

Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.

The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.

2 · The registry

The trial behind it

Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.

NCT05450952 naterminatednot on this mapstarted 2022, after this paper: background citation

A Double-blind, Randomized, Placebo-controlled Study to Evaluate the Effects of a Theanine Formulation on Stress, Burnout, Mood, and Sleep in Individuals Who Report Occasional Moderate or High Levels of Stress

TypeinterventionalSponsorSupplement Formulators, Inc.Ran2022 to 2022Enrolled14ConditionsStressArmsTheanine Formulation, Placebo
NCT05854017 nacompletednot on this mapstarted 2023, after this paper: background citation

A Double-blind, Randomized, Placebo-controlled Study to Evaluate the Effects of a Theanine for Stress Relief Formulation on Stress, Burnout Component, Mood, and Sleep in Individuals Who Report Occasional Moderate or High Levels of Stress

TypeinterventionalSponsorSupplement Formulators, Inc.Ran2023 to 2025Enrolled104ConditionsStressArmsTheanine for stress relief formulation, Placebo
3 · Its place in the literature

Who cites it

51 citing papers in PubMed, 4 syntheses or guidelines pooled it, 177 citations in OpenAlex.

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  2. The Effects of Caffeine on Anxiety Behavior in Healthy Individuals: A Systematic Review of the Literature.Stress and health : journal of the International Society for the Investigation of Stress · 2026
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  14. Association of the anxiogenic and alerting effects of caffeine with ADORA2A and ADORA1 polymorphisms and habitual level of caffeine consumption.Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology · 2010
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4 · The record

Corrections and comments

PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.

5 · Who and what money

Authors and funding

4 authors at 1 institution in 1 country.

Peter J RogersDepartment of Experimental Psychology, University of Bristol, 12a Woodland Road, Bristol, BS8 1TU, UK. Peter.Rogers@bristol.ac.uk
Jessica E Smith
Susan V Heatherley
C W Pleydell-Pearce
University of Bristol · GB

Funding

No grant is acknowledged in the PubMed record.

6 · The paper itself

Abstract

rationaleAlthough both contain behaviourally significant concentrations of caffeine, tea is commonly perceived to be a less stimulating drink than coffee. At least part of the explanation for this may be that theanine, which is present in tea but not coffee, has relaxing effects. There is also some evidence that theanine affects cognitive performance, and it has been found to reduce blood pressure in hypertensive rats.

objectivesTo study the subjective, behavioural and blood pressure effects of theanine and caffeine administered alone and together, in doses relevant to the daily tea consumption of regular tea drinkers. MATERIALS AND

methodsIn a randomised, double-blind, placebo-controlled study, healthy adult participants (n = 48) received either 250-mg caffeine, 200-mg theanine, both or neither of these. They completed ratings of mood, including anxiety, and alertness, and had their blood pressure measured before and starting 40 min after drug administration. Anxiety was also assessed using a visual probe task.

resultsCaffeine increased self-rated alertness and jitteriness and blood pressure. Theanine antagonised the effect of caffeine on blood pressure but did not significantly affect jitteriness, alertness or other aspects of mood. Theanine also slowed overall reaction time on the visual probe task.

conclusionsTheanine is a physiologically and behaviourally active compound and, while it is unclear how its effects might explain perceived differences between tea and coffee, evidence suggests that it may be useful for reducing raised blood pressure.

Indexed as

TeaAdultAffectArousalAttentionBlood PressureCaffeineCognitionDiscrimination LearningDouble-Blind MethodFacial ExpressionFemaleGlutamatesHeart RateHumansMaleCaffeineGlutamatesTeatheanine

Identifiers

PMID17891480
OpenAlexW2073766890

What OpenQuestion holds

Textmetadata
Read underepoch 390

Registered trials

Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.