Caffeine-induced enhancement of cognitive performance: Confounding due to reversal of withdrawal effects

Caffeine has long been thought to have beneficial effects on performance. However, the double-blind placebo-controlled trials typically employed to examine caffeine effects fail to take account of the fact that caffeine is part of the daily diet of most people and that withdrawal effects occur even after brief abstinence (e.g., overnight). Recent empirical findings support the conclusion that improvements in performance following caffeine ingestion do not represent net benefits, but are due to reversal of abstinence-induced withdrawal effects. The claim by Lyvers et al. (2004) in Australian Journal of Psychology that their findings did not support the withdrawal reversal hypothesis is unjustified, because that study included no adequate control for withdrawal reversal.