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Effects of caffeine in non-withdrawn volunteers.

Christopher G, Sutherland D, Smith A

Centre for Occupational and Health Psychology, Cardiff University, 63 Park Place, Cardiff CF10 3AS, UK.

RATIONALE: Evidence for the behavioural effects of caffeine is prevalent in the literature. It is associated with increased subjective alertness, improved reaction time and enhanced encoding of new information. However, there is an on-going debate as to whether such changes are in fact improvements or merely a reversal of the negative effects of caffeine withdrawal. Using participants who had consumed their normal daily quota of caffeine this study alleviated this potential confound as all participants were not withdrawn at the time of testing. OBJECTIVES: To determine whether caffeine influenced the mood and performance of non-withdrawn volunteers. METHODS: Sixty eight volunteers, all of whom were regular caffeine consumers, consumed their normal amount of caffeine over the course of the day. Baseline measures of mood and performance were then carried out followed by double-blind administration of caffeine (2 mg/kg) or placebo. The test battery was repeated again 30 min after ingestion of the drink. RESULTS: Our findings showed improvements comparable to previous research. Mood was improved and performance on a number of cognitive measures was improved. The findings are discussed in relation to both noradrenergic and cholinergic neurotransmitter systems. CONCLUSIONS: This study provided evidence against the argument that behavioural changes due to caffeine are merely the reversal of negative withdrawal effects.

Published 29 December 2004 in Hum Psychopharmacol, 20(1): 47-53.
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