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dc.contributor.authorHewlett, Paul
dc.contributor.authorSmith, Andrew
dc.date.accessioned2017-11-24T16:05:29Z
dc.date.available2017-11-24T16:05:29Z
dc.date.issued2007
dc.identifier.citationHewlett, P. and Smith, A. (2007) 'Effects of repeated doses of caffeine on performance and alertness: new data and secondary analyses', Human Psychopharmacology: Clinical and Experimental, 22(6), pp.339-350.en_US
dc.identifier.issn0885-6222
dc.identifier.urihttp://hdl.handle.net/10369/9151
dc.descriptionThis article was published in Human Psychopharmacology available at http://dx.doi.org/10.1002/hup.854en_US
dc.description.abstractRationale 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 were 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to determine whether caffeine withdrawal influenced mood and performance by comparing regular consumers who had been withdrawn from caffeine overnight with non-consumers.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 a data collected by Christopher et al. (2003) 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 thirty six of the sample did not regularly consume caffeinated beve rages. 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 1mg/kg caffeine in a milkshake, glucose solution or water (at 09:00), followed by a second 0 or 1mg/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 caffe ine consumption.en_US
dc.language.isoenen_US
dc.publisherWileyen_US
dc.relation.ispartofseriesHuman Psychopharmacology;22
dc.subjectCaffeine, Repeated Doses, Mood, Cognitive Performance.en_US
dc.titleEffects of Reapeated Doses of Caffeine on Performance and Alertness: New Data and Secondary Analysesen_US
dc.typeArticleen_US
dc.identifier.doihttp://dx.doi.org/10.1002/hup.854
dcterms.dateAccepted2007-05
rioxxterms.funderCardiff Metropolitan Universityen_US
rioxxterms.identifier.projectCardiff Metropolian (Internal)en_US
rioxxterms.versionAMen_US
rioxxterms.licenseref.urihttp://www.rioxx.net/licenses/all-rights-reserveden_US
rioxxterms.licenseref.startdate2017-11-24
rioxxterms.funder.project37baf166-7129-4cd4-b6a1-507454d1372een_US


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