Caffeine Study Finds No Performance Enhancement

Cup of TeaA study published this month in Neuropsychobiology has found that sustained caffeine use has no significant enhancing effects on performance or mood and does not provide a restorative effect after poor sleep. So are the approximately 90% of us who feel we get a boost from caffeine, just deluding ourselves?

Research into caffeine has produced mixed results. Previous studies have shown some associations between caffeine intake and increased alertness, vigilance and lower levels of fatigue – as we might expect. Even so, some researchers have found that the apparent benefits of caffeine are only seen in individuals who already use the drug. Those not already caffeine users show much smaller improvements. Other studies, however, have found different patterns.

This study differs from many previously carried out by controlling for the effects of caffeine withdrawal. What it suggests is that these types of apparent enhancements are more the result of the alleviation of caffeine withdrawal. Caffeine withdrawal has already been recognised as a kind of disorder causing certain predictable symptoms including drowsiness, headaches and negative mood. It is the association in our minds between the alleviation of caffeine withdrawal symptoms and our morning cup of coffee that keep us coming back for more.

What studies like this suggest is that, overall, our cognitive functions are no more highly tuned if we use drinks containing caffeine than if we abstain completely. In fact there was some evidence found here that caffeine might actually be undermining the restorative effects of sleep.

There has been evidence from epidemiological studies of the long-term benefits of caffeine consumption – such as protection from cancer – but these are, at best, fairly speculative. Equally, caffeine does raise blood pressure and increase the risk of coronary heart disease and strokes.

The findings of this study are a blow to the perception that caffeinated drinks provide a boost to mental performance. After all, most people don’t drink tea or coffee for the long-term health benefits – they just want to wake up.

A word of warning to those inspired to give up: breaking a habit as ingrained as drinking tea or coffee can be difficult and it has been shown that a stepped approach is best. The symptoms of complete caffeine withdrawal can last up to 7 days and are not pleasant if experienced in one go. I know, I’ve tried it.

Dietary Caffeine, Performance and Mood: Enhancing and Restorative Effects after Controlling for Withdrawal Reversal [Article abstract]



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Dr Jeremy Dean is a psychologist and the author of PsyBlog. His latest book is "Making Habits, Breaking Habits: How to Make Changes That Stick". You can follow PsyBlog by email, by RSS feed, on Twitter and Google+.

Published: 23 July 2005

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