|dc.identifier.citation||Hewlett, 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.description||This article was published in Human Psychopharmacology available at http://dx.doi.org/10.1002/hup.854||en_US
|dc.description.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 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withdrawn from caffeine overnight with non-consumers.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.subject||Caffeine, Repeated Doses, Mood, Cognitive Performance.||en_US
|dc.title||Effects of Reapeated Doses of Caffeine on Performance and Alertness: New Data and Secondary Analyses||en_US
|rioxxterms.funder||Cardiff Metropolitan University||en_US
|rioxxterms.identifier.project||Cardiff Metropolian (Internal)||en_US