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

Study Overview
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Brief Summary
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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.

Detailed Description
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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, standard deviation 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.

Official Title
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Levels of Caffeine Lower Than Those Found in Decaffeinated Beverages Exert Effects on Cognition, Mood, and Autonomic Activity

Conditions
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Healthy

Intervention / Treatment
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* Drug: caffeine
* Drug: Placebo


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: native English speaker Exclusion Criteria: pregnancy medication anaemia heart disorder diabetes respiratory disorder epilepsy asthma panic attacks habitual smoking food allergy

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 35 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Placebo Comparator: Placebo<br> | Drug: Placebo<br> <br> |
| Experimental: 2.5mg caffeine<br> | Drug: caffeine<br> <br> |
| Experimental: 5mg caffeine<br> | Drug: caffeine<br> <br> |
| Experimental: 10mg caffeine<br> | Drug: caffeine<br> <br> |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change from baseline speed of attention |  | 1 hour | 
| Change from baseline speed of attention |  | 3 hours | 
| Change from baseline speed of attention |  | 6 hours | 
| Change from baseline speed of attention |  | 9 hours | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change from baseline accuracy of attention |  | 1 hour | 
| Change from baseline accuracy of attention |  | 3 hours | 
| Change from baseline accuracy of attention |  | 6 hours | 
| Change from baseline accuracy of attention |  | 9 hours | 
| Change from baseline speed of memory |  | 1 hour | 
| Change from baseline speed of memory |  | 3 hours | 
| Change from baseline accuracy of memory |  | 6 hours | 
| Change from baseline accuracy of memory |  | 9 hours | 
| Change from baseline subjective mood |  | 1 hour | 
| Change from baseline subjective mood |  | 3 hours | 
| Change from baseline subjective mood |  | 6 hours | 
| Change from baseline subjective mood |  | 9 hours | 
| Change from baseline blood pressure |  | 1 hour | 
| Change from baseline blood pressure |  | 3 hours | 
| Change from baseline blood pressure |  | 6 hours | 
| Change from baseline blood pressure |  | 9 hours | 
| Change from baseline heart rate |  | 1 hour | 
| Change from baseline heart rate |  | 3 hours | 
| Change from baseline heart rate |  | 6 hours | 
| Change from baseline heart rate |  | 9 hours | 
| Change from baseline salivary caffeine levels |  | 1 hour | 
| Change from baseline salivary caffeine levels |  | 3 hours | 
| Change from baseline salivary caffeine levels |  | 6 hours | 
| Change from baseline salivary caffeine levels |  | 9 hours | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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caffeine, coffee, decaffeinated, cognition, mood, autonomic