[InSteady]

A lot of the back and forth in this thread seems to be overlooking the glaring fact that caffeine's half-life varies from 2 to 12 hours depending on the person. Getting to 90% elimination could take one person ~6 hours and another person ~36 hours.

This, on top of the fact that caffeine has been shown to increase cortisol secretion and adrenaline, as well as boosting the effects of dopamine and norepinephrine in the brain, should give a very clear indication that caffeine is going to have drastically different effects from person to person.

Anyone who is struggling with sleep, anxiety, and/or mood disturbances should consider reducing or eliminating caffeine for several weeks to see if it helps. Don't expect it to be a magic bullet to solve all problems, just like anything else. Bodies are complex, and when we are chronically suffering from sub-optimal functioning, it's a good bet that their is some complicated and highly variable biochemistry going on that's keeping the body from homeostasis / optimum function.