Overview

• Two ecological momentary assessment studies of 236 young adults produced nearly 28,000 brief reports over several weeks, with results published in Scientific Reports by teams at the Universities of Bielefeld and Warwick.
• Mood improvements peaked roughly within the first two to two-and-a-half hours after waking and diminished later in the day.
• Participants reported increases in positive emotions such as happiness, enthusiasm and satisfaction, while changes in negative feelings like sadness or anger were smaller or inconsistent across studies.
• The uplift was stronger in very tired individuals and when coffee was consumed alone rather than in social situations.
• Authors note that relief of overnight caffeine withdrawal may contribute to the morning effect, and they caution that findings rely on young, self-reported samples and that excessive caffeine can disturb sleep or promote dependence.