Effects of caffeine and caffeine withdrawal on mood and cognitive performance degraded by sleep restriction.
BACKGROUND
It has been suggested that caffeine is most likely to benefit mood and performance when alertness is low.


OBJECTIVE
To measure the effects of caffeine on psychomotor and cognitive performance, mood, blood pressure and heart rate in sleep-restricted participants. To do this in a group of participants who had also been previously deprived of caffeine for 3 weeks, thereby potentially removing the confounding effects of acute caffeine withdrawal.


METHODS
Participants were moderate to moderate-high caffeine consumers who were provided with either decaffeinated tea and/or coffee for 3 weeks (LTW) or regular tea and/or coffee for 3 weeks (overnight caffeine-withdrawn participants, ONW). Then, following overnight caffeine abstinence, they were tested on a battery of tasks assessing mood, cognitive performance, etc. before and after receiving caffeine (1.2 mg/kg) or on another day after receiving placebo.


RESULTS
Final analyses were based on 17 long-term caffeine-withdrawn participants (LTW) and 17 ONW participants whose salivary caffeine levels on each test day confirmed probable compliance with the instructions concerning restrictions on consumption of caffeine-containing drinks. Acute caffeine withdrawal (ONW) had a number of negative effects, including impairment of cognitive performance, increased headache, and reduced alertness and clear-headedness. Caffeine (versus placebo) did not significantly improve cognitive performance in LTW participants, although it prevented further deterioration of performance in ONW participants. Caffeine increased tapping speed (but tended to impair hand steadiness), increased blood pressure, and had some effects on mood in both groups.


CONCLUSIONS
The findings provide strong support for the withdrawal reversal hypothesis. In particular, cognitive performance was found to be affected adversely by acute caffeine withdrawal and, even in the context of alertness lowered by sleep restriction, cognitive performance was not improved by caffeine in the absence of these withdrawal effects. Different patterns of effects (or lack of effects) of caffeine and caffeine withdrawal were found for other variables, but overall these results also suggest that there is little benefit to be gained from caffeine consumption.
Rogers
Peter J
PJ
Department of Experimental Psychology, University of Bristol, 8 Woodland Road, Bristol, BS8 1TN, UK. Peter.Rogers@bristol.ac.uk
Heatherley
Susan V
SV
Hayward
Robert C
RC
Seers
Helen E
HE
Hill
Joanne
J
Kane
Marian
M
D000328:Adult; D000339:Affect / Q000187:drug effects*; D001288:Attention / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D002110:Caffeine / Q000009:adverse effects* / Q000493:pharmacokinetics / Q000494:pharmacology*; D000697:Central Nervous System Stimulants / Q000009:adverse effects* / Q000493:pharmacokinetics / Q000494:pharmacology*; D002851:Chromatography, High Pressure Liquid; D003071:Cognition / Q000187:drug effects*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007124:Immunoenzyme Techniques; D007175:Impulsive Behavior / Q000523:psychology; D008297:Male; D008568:Memory / Q000187:drug effects; D008570:Memory, Short-Term / Q000187:drug effects; D011597:Psychomotor Performance / Q000187:drug effects / Q000502:physiology; D011930:Reaction Time / Q000187:drug effects; D012892:Sleep Deprivation / Q000523:psychology*; D013375:Substance Withdrawal Syndrome / Q000378:metabolism / Q000523:psychology*; D014202:Tremor / Q000523:psychology
D000697:Central Nervous System Stimulants; D002110:Caffeine