According to this study, during periods when participants' sleep schedules were more varied, participants were more likely to report symptoms of depression in their quarterly questionnaires. They also reported a worse mood every day.
Interestingly, they fared no better than the participants who slept less than they did, even if they slept adequately when they went to bed and woke up at different times each day.
As professor and co-author of the study Srijan Sen, M.D., Ph.D. summarizes in a press release on the study: "These results underscore sleep consistency as an underrated factor that plays a role in depression and well-being."
This shows with which sleep and health psychologist Joshua Tal, Ph.D. previously told mbg: "It's really important to keep a consistent sleep schedule […] as our natural circadian rhythms can be a bit confused if we keep changing our sleep schedule." And a confused daily rhythm can make a good mood unattainable.
Going forward, the Michigan research team hopes their results can be extended to the more general population as we continue to better understand how sleep and mental health are related.