Overview
- Smartphone-based assessments of 236 habitual caffeine users over up to four weeks found higher positive emotions after the first caffeinated drink compared with similar times without caffeine.
- The uplift was most pronounced in the first hours after waking, peaking within roughly 2.5 hours.
- Tired participants reported larger gains, and the effect was stronger when drinking alone than in social settings.
- Changes in negative emotions were smaller or inconsistent, and part of the benefit may reflect relief from mild overnight withdrawal in regular consumers.
- Authors note limits—young, mostly female sample and self-reports only—and reiterate cautions about excessive caffeine, including sleep disruption, nervousness, palpitations and dependence.