it's a very real physiological reaction to caffeine. I took some aspirin/caffeine tablets once for a headache.. i wasn't aware of the additional caffeine conten

it's a very real physiological reaction to caffeine. I took some aspirin/caffeine tablets once for a headache.. i wasn't aware of the additional caffeine content (a few cups of coffee worth) , but was an anxious mess an entire night, heart racing, didn't sleep. Coffee has a smaller but similar effect.