The University of Michigan conducted research to reveal something we already know but rarely acknowledge: sleep is linked to our happiness and overall moods. In today’s world, getting sufficient sleep feels unattainable because there are so many demands on our time, often leading us to sacrifice rest. The research reached this conclusion by analyzing FitBit data, a device commonly used in daily life. The researchers were working on the Intern Health Study Project, where interns wore fitness trackers like FitBit to monitor their activity, heart rate, and sleep habits. The interns, who were first-year training physicians, were studied to observe how pressure and work affect their overall health.
Some algorithms were developed by researchers, extracting quantitative information about sleep cycles, circadian rhythms, and other activities of the participants. Participants also completed mood surveys consistently. The circadian clock, located in the suprachiasmatic nuclei of the brain, controls the 24-hour cycle of mental, physical, and behavioral changes in the body. In this study, researchers examined the heart’s circadian clock, known as the peripheral clock, to understand how it prepares energy for the body throughout the day. Typically, this clock prepares energy for greater activity at 2 p.m. rather than 2 a.m. The research found that when the interns’ sleep cycles were out of sync with the heart's peripheral clock, it negatively impacted their mood.
The interns experienced depressive symptoms, such as loss of appetite, and insomnia, when their circadian clocks and sleep cycles were misaligned. These symptoms were more prominent during work due to disrupted central circadian clocks, which affected their overall mood. The study revealed that misaligned sleep cycles and circadian rhythms could severely impact both mood and health. Sleep quantity also affects mental health, with adequate rest having positive effects. However, this doesn’t mean mental health challenges, such as depression, can be entirely resolved through better sleep alone. Happiness is influenced by various external factors that can also affect mood.
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