Ann Arbor Times

A recent study conducted by the University of Michigan highlights the impact of sleep alignment with internal circadian rhythms on mood. The research, published in npj Digital Medicine, indicates that when sleep cycles are misaligned with these rhythms, it can significantly affect emotional well-being.

Senior author Daniel Forger stated, "This is not going to solve depression. We need to be very, very clear about that." He emphasized the importance of understanding individual sleep patterns and circadian rhythms as a controllable factor affecting mood.

The study utilized data from the Intern Health Study, which involves first-year training physicians wearing fitness trackers like Fitbits. These devices monitor heart rate, activity, and sleeping habits while participants complete routine mood surveys. This project received support from both the National Institutes of Health and the National Science Foundation.

Forger's team developed algorithms to analyze Fitbit data and assess individuals' circadian rhythms and sleep cycles. They found significant links between these alignments and mental health measures using tools such as the PHQ-9 questionnaire. "When people start to get desynchronized, we see the PHQ-9 go up, on average, by 2.5," Forger noted.

Lead author Minki Lee pointed out that it's not just about going to bed earlier but aligning sleep schedules with internal rhythms. The study identified three important patterns: the central circadian clock in the brain's suprachiasmatic nuclei, peripheral clocks like those in the heart, and interns' sleep cycles.

Dae Wook Kim highlighted that misalignment between central circadian clocks and sleep had a strong negative association with mood during shift work. "These findings challenge prior assumptions about the uniform impact of circadian disruptions across different physiological clocks," Kim said.

The researchers aim to extend their methodology to other groups such as students and older adults. As Lee mentioned, context matters since lifestyle factors like exams or travel can influence how disruptions affect mood.

Forger concluded that technology like fitness trackers could help many people understand when rest is needed to counteract these disruptions: "That's why this is scalable," he said.