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Effects of repeated doses of caffeine on performance and alertness: new data and secondary analyses.
Hum Psychopharmacol 2007; 22(6):339-50HP

Abstract

RATIONALE

The effects of caffeine on mood and performance are well established. Some authors suggest that caffeine merely reverses effects of caffeine withdrawal rather than having direct behavioural effects. It has also been suggested that withdrawal may be removed by a first dose of caffeine and further doses have little subsequent effect. These issues are examined here.

OBJECTIVES

The present study aimed to determine whether caffeine withdrawal influenced mood and performance by comparing regular consumers who had been withdrawn from caffeine overnight with non-consumers. Following this repeated caffeine doses were administered to test the claim that repeated dosing has no extra effect on mood or performance. Secondary analyses of data collected after a day of normal caffeine consumption were also carried out to examine some alternative explanations of their results which showed effects of caffeine after a day of normal caffeine consumption.

METHODS

One hundred and twenty volunteers participated in the study. Regular caffeine consumption was assessed by questionnaire and this showed that 36 of the volunteers did not regularly consume caffeinated beverages. Volunteers were instructed to abstain from caffeine overnight and then completed a baseline session measuring mood and a range of cognitive functions at 08.00 the next day. Following this volunteers were given 0, or 1 mg/kg caffeine in a milkshake, glucose solution or water (at 09:00), followed by a second 0 or 1 mg/kg caffeine dose (at 09:40) and the test battery repeated at 10:00.

RESULTS

The baseline data showed no effect of overnight caffeine withdrawal on mood or performance. In contrast, caffeine challenge improved vigilance performance and prevented decreases in alertness induced by completion of the task battery. The magnitude of these effects increased as a function of the number of doses of caffeine given. Secondary analyses of data from Christopher et al. (2003) also confirmed that effects of caffeine did not depend on length of withdrawal.

CONCLUSIONS

The present findings show no effect of overnight caffeine withdrawal on mood and performance. Caffeine challenge did have the predicted effect on alertness and vigilance, with the size of the effects increasing with caffeine dose. These findings suggest that the effects of caffeine are not due to reversal of effects of withdrawal, a view confirmed by secondary analyses of data collected after a day of normal caffeine consumption.

Authors+Show Affiliations

Centre for Occupational and Health Psychology, School of Psychology, Cardiff University, 63 Park Place, Cardiff, UK.No affiliation info available

Pub Type(s)

Comparative Study
Journal Article

Language

eng

PubMed ID

17514640

Citation

Hewlett, Paul, and Andrew Smith. "Effects of Repeated Doses of Caffeine On Performance and Alertness: New Data and Secondary Analyses." Human Psychopharmacology, vol. 22, no. 6, 2007, pp. 339-50.
Hewlett P, Smith A. Effects of repeated doses of caffeine on performance and alertness: new data and secondary analyses. Hum Psychopharmacol. 2007;22(6):339-50.
Hewlett, P., & Smith, A. (2007). Effects of repeated doses of caffeine on performance and alertness: new data and secondary analyses. Human Psychopharmacology, 22(6), pp. 339-50.
Hewlett P, Smith A. Effects of Repeated Doses of Caffeine On Performance and Alertness: New Data and Secondary Analyses. Hum Psychopharmacol. 2007;22(6):339-50. PubMed PMID: 17514640.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Effects of repeated doses of caffeine on performance and alertness: new data and secondary analyses. AU - Hewlett,Paul, AU - Smith,Andrew, PY - 2007/5/22/pubmed PY - 2007/10/24/medline PY - 2007/5/22/entrez SP - 339 EP - 50 JF - Human psychopharmacology JO - Hum Psychopharmacol VL - 22 IS - 6 N2 - RATIONALE: The effects of caffeine on mood and performance are well established. Some authors suggest that caffeine merely reverses effects of caffeine withdrawal rather than having direct behavioural effects. It has also been suggested that withdrawal may be removed by a first dose of caffeine and further doses have little subsequent effect. These issues are examined here. OBJECTIVES: The present study aimed to determine whether caffeine withdrawal influenced mood and performance by comparing regular consumers who had been withdrawn from caffeine overnight with non-consumers. Following this repeated caffeine doses were administered to test the claim that repeated dosing has no extra effect on mood or performance. Secondary analyses of data collected after a day of normal caffeine consumption were also carried out to examine some alternative explanations of their results which showed effects of caffeine after a day of normal caffeine consumption. METHODS: One hundred and twenty volunteers participated in the study. Regular caffeine consumption was assessed by questionnaire and this showed that 36 of the volunteers did not regularly consume caffeinated beverages. Volunteers were instructed to abstain from caffeine overnight and then completed a baseline session measuring mood and a range of cognitive functions at 08.00 the next day. Following this volunteers were given 0, or 1 mg/kg caffeine in a milkshake, glucose solution or water (at 09:00), followed by a second 0 or 1 mg/kg caffeine dose (at 09:40) and the test battery repeated at 10:00. RESULTS: The baseline data showed no effect of overnight caffeine withdrawal on mood or performance. In contrast, caffeine challenge improved vigilance performance and prevented decreases in alertness induced by completion of the task battery. The magnitude of these effects increased as a function of the number of doses of caffeine given. Secondary analyses of data from Christopher et al. (2003) also confirmed that effects of caffeine did not depend on length of withdrawal. CONCLUSIONS: The present findings show no effect of overnight caffeine withdrawal on mood and performance. Caffeine challenge did have the predicted effect on alertness and vigilance, with the size of the effects increasing with caffeine dose. These findings suggest that the effects of caffeine are not due to reversal of effects of withdrawal, a view confirmed by secondary analyses of data collected after a day of normal caffeine consumption. SN - 0885-6222 UR - https://www.unboundmedicine.com/medline/citation/17514640/Effects_of_repeated_doses_of_caffeine_on_performance_and_alertness:_new_data_and_secondary_analyses_ L2 - https://doi.org/10.1002/hup.854 DB - PRIME DP - Unbound Medicine ER -