- history of epilepsy, current episode of major depressive disorder or anxiety disorder, or a current sleep problem or an inability to comprehend English, travel over two time zones within the last six months, excessive alcohol (over 3 units per day) or caffeine consumption (more than 6 caffeinated drinks or 1 after 6pm), a smoker, a shift worker, a familial history of diabetes, users of medication or supplements, or if the participant is pregnant or currently lactating.