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Researchers from the University of Michigan and Dartmouth Health analyzed the Fitbit data from 2,602 medical interns over two years.
“Mood naturally cycles with lowest point in the morning and highest in the evening independent of sleep deprivation,” explains lead study author Benjamin Shapiro. “Sleep deprivation is a separate process that further decreases mood.” Senior study author Danny Forger adds, “We discovered that mood follows a rhythm connected to the body’s internal clock, and the clock’s influence increases as someone stays awake longer.”