IF that shot of espresso revs you up even though you ordered decaf, don't accuse the server of giving you the real thing. A Swiss study has found that occasional coffee drinkers get a buzz from decaf – their systolic blood pressure (the first number) goes up and their nervous system is stimulated.
One of the other components of coffee, not the caffeine, is the likely cause, conclude University of Zurich researchers. Regular coffee drinkers don't get the same lift in blood pressure even after drinking the real thing, probably because they've developed a tolerance.