Dietary Caffeine, Performance and Mood: Enhancing and Restorative Effects after Controlling for Withdrawal Reversal

Abstract

This study aimed to determine whether sustained (i.e. dietary) use of caffeine has net effects on performance and mood compared with sustained abstinence, and whether dietary caffeine restores performance and mood adversely affected by sleep restriction. Participants (n = 96) alternated weekly between ingesting placebo and caffeine (1.75 mg/kg) three times daily for 4 consecutive weeks, while either rested or sleep restricted. Performance involved either a single task requiring sustained vigilance or a varied battery of brief psychomotor and cognitive tasks, and mood was assessed using the Profile of Mood States. Caffeine had no significant net enhancing effects for either performance or mood when participants were rested, and produced no net restorative effects when performance and mood were degraded by sleep restriction.

Effects of Dietary Caffeine on Topographic EEG after Controlling for Withdrawal and Withdrawal Reversal

“…Whereas a number of previous studies found decrements in performance associated with caffeine withdrawal and reversal of performance decrements when caffeine is re-ingested [23,38,45,46,59] , no such withdrawal and reversal of withdrawal effects were observed during task performance in the present study. The absence of caffeine-induced performance effects in the present study could have been due to the presence of ceiling effects.…”

“…The extended paradigm and versions of it have been employed in various studies of caffeine-induced effects on performance, mood, cardiovascular reactivity, and sleep [23,41,42,[44][45][46] . The paradigm includes four consecutive 1-week periods ( table 1 ), with a strictly prescribed and biologically verified regimen of caffeine intake or abstinence for every day of each week.…”

“…Alkaysi et al [50] have shown that caffeine concentrations in blood and saliva are highly correlated, and saliva was chosen as the preferred matrix in the present and previous studies [41,45,46] because of ease of collection. Caffeine levels generally rise progressively throughout the day due to intermittent consumption of caffeine beverages, and plateau in the late afternoon and early evening after the last beverage of the day has been consumed.…”

“…Following a procedure we have used previously [23,41,45,46] , participants were asked whether 'you think you had' caffeine or placebo during the 6-day run-in period and during the laboratory session itself. Guesses were recorded, and participants were allowed to revise their guesses as the study progressed.…”

Neuroenhancement in Healthy Adults, Part I: Pharmaceutical Cognitive Enhancement: A Systematic Review

“…Surprisingly, we found no meta-analysis on caffeine cognitive effects in healthy adults. In a review, James et al [161] concluded that appropriately controlled studies show that its apparent beneficial effects on performance and mood are almost wholly attributable to reversal of the withdrawal effects that occur after short periods of abstinence (e.g. overnight).…”