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Link between sleep and mood explains the "wrong side of the bed"

Have you ever hit snooze ten times, muttering about waking up on the “wrong side of the bed”? Turns out, that grumpy feeling might not be just your imagination. A new study by the University of Michigan and Dartmouth Health explains the connection behind our mood and sleep timing.

Sleep-deprived medical interns, notorious for their grueling schedules, offered a goldmine of data for this two-year study. The researchers combed through Fitbit data from over 2,500 of these interns to reveal their mood pattern.

Mood swings and sleep

Here’s the surprising finding: everyone’s mood naturally dips in the early morning hours, around 5 am. Interestingly, this low point happens regardless of how much sleep you get. It is your body’s built-in grump phase.

However, sleep deprivation makes this natural dip even worse. So, if you pull an all-nighter, that 5 am low point feels even lower.

“Mood naturally cycles with lowest point in the morning and highest in the evening independent of sleep deprivation,” explained Benjamin Shapiro, lead author of the study and psychiatrist at Dartmouth Health.

Sleep patterns affecting mood

The study revealed a connection between our internal body clock, called the circadian rhythm, and our moods. This internal clock runs on a 24-hour cycle and manages essential bodily functions.

The study suggests that our feelings of happiness, sadness, and irritability are not random, but instead follow a predictable pattern throughout the day and night.

“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,” explained Danny Forger, a senior author of the study.

Disruptions to our circadian rhythm, caused by shift work, jet lag, or irregular sleep, can significantly impact our mood. The mismatch between our internal clock and the external environment throws off the natural rhythm of mood-regulating processes.

Study significance

What sets this study apart is its application to real-life settings, moving beyond the controlled environments of traditional laboratory studies. “The field of psychiatry has known that sleep and circadian rhythm play an important role in mental health,” said Shapiro.

“However, these findings have only been shown in small samples and in artificial laboratory settings.” This research extends those insights to a broader, more diverse population, highlighting the everyday relevance of sleep on our mental health.

An exciting takeaway from the study is the potential for wearable technology, like Fitbits, to revolutionize the monitoring and treatment of mood disorders.

“Rather than requiring invasive blood draws or temperature monitoring, we are able to obtain similar data from an everyday Fitbit,” Shapiro noted.

This opens new avenues for mental health clinicians to incorporate circadian rhythm metrics into their practices, making mental health care more accessible and integrated into our daily lives.

Mental health care

The study not only sheds light on why we might feel particularly gloomy in the mornings but also heralds a new era in mental health care. By leveraging the technology we wear every day, we’re on the brink of better understanding and managing our mood cycles.

So, the next time you wake up feeling like you’ve picked a fight with the sunrise, remember: it’s not just you, it’s science. And thanks to the diligent work of researchers, we’re getting closer to turning every side of the bed into the right one.

The study is published in the journal PLOS Digital Health.


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