Effects of repeated doses of caffeine on performance and alertness: new data and secondary analyses

Abstract

RationaleThe 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to determine whether caffeine withdrawal influenced mood and performance by comparing regular consumers who had been withdrawn from caffeine overnight with non-consumers.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. ResultsThe 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. ConclusionsThe present findings show no effect of overnight caffeine withdrawal on mood and performance. Caffeine challenge did have the predicted effect on alertness and v igilance, 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.

Glucose and caffeine effects on sustained attention: an exploratory fMRI study.

“…Therefore, the apparent effects of caffeine might in fact reflect withdrawal reversal. Although some studies give support to this hypothesis (James and Rogers, 2005;Rogers et al, 2003;Rogers et al, 2005), the majority of studies support the idea that caffeine has psychoactive effects even in the absence of withdrawal (Childs and de Wit, 2006;Christopher et al, 2005;Haskell et al, 2005;Hewlett and Smith, 2006;Hewlett and Smith, 2007).…”

Acute effects of brewed cocoa consumption on attention, motivation to perform cognitive work and feelings of anxiety, energy and fatigue: a randomized, placebo-controlled crossover experiment

“…Improved accuracy and fewer omission errors on the primary Bakan task occurred after the caffeine alone condition but the effect was smaller. Caffeine can improve vigilance performance by improving accuracy, reducing errors and reducing reaction time [46,47] so it is unclear why the effects of supplemental caffeine were limited to the primary task of the Bakan test. One possibility is that the participants in the present study were not especially responsive to the mood, motivation and attention enhancing influence of caffeine.…”

Caffeine, Mental Health, and Psychiatric Disorders

“…Some studies with low doses of caffeine (50-100 mg) suggest that most effects are due to withdrawal reversion in regular users [19,20]. However, other studies in volunteers without caffeine withdrawal, either by long term abstinence or ongoing caffeine use, showed significant effects of caffeine on performance, alertness, and mood [21][22][23]. Moreover, a recent study [24] found that in light, nondependent caffeine users (mean 116 mg/week) caffeine produced increased energy, vigour, and arousal and less fatigue at 150 mg, but not 50 mg. Anxiety increased with 450 mg but not with 150 mg or 50 mg. Caffeine also failed to produce reinforcing effects of "liking" and "wanting more" at any dose, contrary to d-amphetamine.…”