Effects of Low Doses of Caffeine on Mood, Physiology and Mental Function

This study has been completed.
Information provided by:
Northumbria University
ClinicalTrials.gov Identifier:
First received: June 15, 2007
Last updated: NA
Last verified: June 2007
History: No changes posted

It is often assumed that levels of caffeine found in ‘decaffeinated’ beverages are below any psychopharmacological threshold. However, recent findings indicate that caffeine doses as low as 9 mg may be psychoactive. The effects of caffeine have also been shown up to 6 hours post-administration. The study aimed to establish the lowest active dose of caffeine, and to ascertain the duration of any effects.

Condition Intervention
Drug: caffeine

Study Type: Interventional
Study Design: Allocation: Randomized
Endpoint Classification: Efficacy Study
Intervention Model: Crossover Assignment
Masking: Double-Blind
Primary Purpose: Basic Science
Official Title: Levels of Caffeine Lower Than Those Found in Decaffeinated Beverages Exert Effects on Cognition, Mood, and Autonomic Activity

Resource links provided by NLM:

Further study details as provided by Northumbria University:

Primary Outcome Measures:
  • Assessment of memory, attention, reaction time and subjective mood, measurement of heart rate and blood pressure. Co-monitoring of salivary caffeine levels. [ Time Frame: baseline, 1 hour, 3 hours, 6 hours and 9 hours ]

Enrollment: 20
Study Start Date: June 2005
Study Completion Date: November 2005
Detailed Description:

The majority of recent caffeine studies have evaluated doses in the range of 75 – 150 mg or 1 – 2 mg/kg (approximately 130 - 260 ml fresh coffee). Such doses produce well characterised effects; including increased ‘alertness’, and improvements to measures of reaction time and sustained attention. A previous study has demonstrated improvements to performance following 9 mg caffeine, which represents the lowest known psychoactive dose of caffeine. A number of these effects, including elevated salivary caffeine levels, were still apparent at 6 hours post-caffeine consumption (9). Findings showing effects of 12.5 and 9 mg caffeine are important as these are approaching the levels found in decaffeinated beverages, which are assumed to have no behavioural or physiological effects. However, despite extensive research in this area, the lower threshold for psychoactive effects has not been established. A randomised, placebo-controlled, double-blind, balanced crossover study was undertaken. 20 young men and women (13 female, mean age 20.7 years, SD 2.4) undertook computerised assessments of memory and attention and rated subjective mood. Autonomic activity and salivary caffeine were co-monitored. Assessment took place at baseline, 1, 3, 6, and 9 hours post-administration of placebo, 2.5, 5, and 10 mg caffeine (on separate days) administered in 150 ml fruit juice.


Ages Eligible for Study:   18 Years to 35 Years
Genders Eligible for Study:   Both
Accepts Healthy Volunteers:   Yes

Inclusion Criteria:

  • native English speaker

Exclusion Criteria:

  • pregnancy
  • medication
  • anaemia
  • heart disorder
  • diabetes
  • respiratory disorder
  • epilepsy
  • asthma
  • panic attacks
  • habitual smoking
  • food allergy
  Contacts and Locations
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Please refer to this study by its ClinicalTrials.gov identifier: NCT00487227

Sponsors and Collaborators
Northumbria University
Principal Investigator: Andrew Scholey Northumbria University
  More Information

No publications provided

ClinicalTrials.gov Identifier: NCT00487227     History of Changes
Other Study ID Numbers: 7G2CDCH
Study First Received: June 15, 2007
Last Updated: June 15, 2007
Health Authority: United Kingdom: Northumbria University

Keywords provided by Northumbria University:

Additional relevant MeSH terms:
Central Nervous System Agents
Central Nervous System Stimulants
Enzyme Inhibitors
Molecular Mechanisms of Pharmacological Action
Neurotransmitter Agents
Pharmacologic Actions
Phosphodiesterase Inhibitors
Physiological Effects of Drugs
Purinergic Agents
Purinergic Antagonists
Purinergic P1 Receptor Antagonists
Therapeutic Uses

ClinicalTrials.gov processed this record on August 26, 2015