Everyone knows that if you feel tired, a cup of coffee will pick you up. Or will it? In one recent test, Peter Rogers and his colleagues from the Universities of Bristol, Münster, and Würzburg and from Imperial College London have determined that, contrary to popular opinion, caffeine does not increase alertness.
379 people who had abstained from caffeine for 16 hours were given either a placebo or caffeine. About half of the participants ranked themselves as non/low caffeine users, the other half as medium/high users. They were all questioned about perceived levels of alertness, headache and anxiety both before and after being given their unknown nostrum. In addition, they were physically tested for levels of alertness.
Although the medium/high users reported increased headache and dullness with placebo as compared to with caffeine, their tested level of alertness on caffeine was similar to that of the non/low users on placebo. In other words, the caffeine users were only as alert with caffeine as the nonusers were without it.
The authors interpret this result as meaning that the medium/high caffeine users had been suffering from caffeine withdrawal, and that adding caffeine back after the 16 hour caffeine fast merely brought their alertness levels back up to normal. The nonusers, having suffered no caffeine withdrawal, maintained the same alertness level with or without caffeine.
If these results are true, this implies that people get no benefit beyond placebo when they first start using caffeine as a stimulant, but that they subsequently require caffeine to prevent withdrawal symptoms. Anecdotally, I never found my caffeine consuming friends to be any more alert than my non-caffeine using self.