However, the study, led by Professor Peter Rogers and Dr Lindsay St. Claire at the University of Bristol, also found that men working in teams could feel less stressed after enjoying a sharp intake of caffeine.
Existing theories about stress management suggest that caffeine consumption can trigger stress. However, while studies into the effects of caffeine show that it can sometimes worsen anxiety, there is also evidence that it boosts confidence, alertness and sociability as well as making us better able to perform various tasks.
The Bristol research, which tried to reconcile these different perspectives, was sparked by an anecdote from a man taking part in a stress management workshop, describing a trip to the United States with his small, cohesive business team.
During the trip, he said, coffee was freely available, and the team over-indulged. Within days, stress levels had escalated and they believed that the extra caffeine had disrupted emotional feelings and relationships, and impaired their ability to perform normally.
Aiming to test this theory, the researchers found that caffeine did indeed heighten feelings of stress while performing stressful tasks, but unexpectedly this happened especially in men. However, effects of caffeine on performance were likely to depend on the type of task and whether participants were working alone or in teams.
For example, when working on mental arithmetic alone and under time pressure, caffeine might help, but when working on a collaborative task, it might undermine people's ability to get along with each other.
The study also tested the impact of expectations, or whether someone who chooses to have a cup of coffee, believing it will speed reaction
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Contact: Becky Gammon
becky.gammon@esrc.ac.uk
179-341-3122
Economic & Social Research Council
13-Feb-2004