In the study, caffeine stopped being significant after 2-3 days of 5h sleep compared with placebo. (200mg twice a day, if I read this right?) “Results showed that the caffeinated group had faster reaction times during the first two days compared with the placebo group, but not on the last three days [out of 5] of the experiment, […] The people who took caffeine reported feeling happier than those who took the placebo only on the first few days of the experiment.” + “those in the caffeine group rated themselves more annoyed than those in the placebo group” Study did not increase amount of caffeine