Bristol University researchers found that after going off caffeine for 16 hours, high consumers of caffeine that received a caffeine pill noticed a rise in anxiety, alertness and headache, while those that received a placebo reported a decline. However, the levels to which these subjects felt a rise in alertness was the same as low consumers that received a placebo — essentially suggesting that the caffeine brought them back to normal, pre-addiction levels of alertness.
Photo by David Joyce.
So while an occasional cup of coffee may give you a jolt, regular consumption may just make you go through withdrawal when you don't get your morning cup. If you find that you're just as alert as you were before your caffeinated days, maybe it's time to switch to orange juice.