Effects of caffeine on performance and mood depend on the level of caffeine abstinence.
BACKGROUND
Most studies of the effects of caffeine on performance have used regular caffeine consumers who are deprived at test. Thus the reported effects of caffeine could be explained through reversal of caffeine withdrawal.


OBJECTIVE
To test how preloading deprived caffeine consumers with 0, 1 or 2 mg/kg caffeine altered the subsequent ability of caffeine to modify mood and performance.


METHODS
Thirty moderate caffeine consumers were given a drink containing 0, 1 or 2 mg/kg caffeine at breakfast followed 60 min later by a second drink containing either 0 or 1 mg/kg caffeine. Performance on a measure of sustained attention and mood were measured before and after each drink.


RESULTS
Administration of both 1 and 2 mg/kg caffeine at breakfast decreased reaction time and 1 mg/kg caffeine also increased performance accuracy on the sustained attention (RVIP) task relative to placebo. Both breakfast doses of caffeine also improved rated mental alertness. Similarly, 1 mg/kg caffeine administered 60 min after breakfast decreased reaction time and increased rated mental alertness in the group who had not been given caffeine at breakfast. However, this second dose of caffeine had no effect on subsequent performance or mood in the two groups who had received caffeine at breakfast.


CONCLUSIONS
Caffeine reliably improved performance on a sustained attention task, and increased rated mental alertness, in moderate caffeine consumers who were tested when caffeine-deprived. However, caffeine had no such effects when consumers were no longer caffeine deprived. These data are consistent with the view that reversal of caffeine withdrawal is a major component of the effects of caffeine on mood and performance.
Yeomans
Martin R
MR
Experimental Psychology, University of Sussex, Brighton, UK. martin@biols.sussex.ac.uk
Ripley
Tamzin
T
Davies
Laura H
LH
Rusted
Jennifer M
JM
Rogers
Peter J
PJ
D000328:Adult; D000339:Affect / Q000187:drug effects*; D001288:Attention / Q000187:drug effects*; D002110:Caffeine / Q000008:administration & dosage / Q000494:pharmacology*; D000697:Central Nervous System Stimulants / Q000008:administration & dosage / Q000494:pharmacology*; D003069:Coffee / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D008297:Male; D010919:Placebos; D011597:Psychomotor Performance / Q000187:drug effects; D011930:Reaction Time; D011795:Surveys and Questionnaires; D013997:Time Factors
D000697:Central Nervous System Stimulants; D003069:Coffee; D010919:Placebos; D002110:Caffeine