Circadian dependent changes in mood with caffeine treatment, (a) CAF mice spend a lower percent of their time in the open arms of the elevated plus maze than water mice during the light cycle, suggesting increased anxiety (*P < 0.05 by student’s t-test; control n=15, CAF n=13). (b) Plasma corticosterone measured during the light cycle was significantly higher in CAF than in control mice (*P < 0.05 by student’s t-test; n=5 per group), (c) Immobility time in the forced swim test. Mice who received CAF treatment are not significantly different from control mice during the light cycle, but spend significantly less time immobile during the dark cycle (#P <0.05 for main effect of treatment; *P < 0.05 compared to control by Tukey’s post hoc test; control n=10 and CAF n=9 for light and dark cycle).