Circadian rhythms are cycles of physical, mental, and behavioral changes. They last approximately 24 hours, and they let us know when it’s time to snooze and when to wake up and smell the coffee— no alarm clock necessary. And Enrique isn’t the only one feeling that rhythm divinecircadian rhythms are a basic part of human life.

The Rhythm of the (Day and) Night — The Need-to-Know

Photo by Marissa Angell

Circadian rhythms influence when we’re hungry, happy, and sleepy (and maybe even Dopey, too.) The human body naturally produces chemicals that regulate daily behavior patterns. But environmental cues— especially light and darkness— are also important. Exposure to light tells the body to stay awake, while darkness says break out the blankets. People tend to be least alert between 2 and 6 am, while energy levels generally peak between 6 and 8 pm.

From mood swings to the munchies, circadian rhythms play a role in a range of biological activities. Retweet this: Based on a study of Twitter messages, one group of researchers believes happiness peaks in the morning and around midnightDiurnal and seasonal mood vary with work, sleep, and daylength across diverse cultures. Golder, S.A., Macy, M.W. Department of Sociology, Cornell University, Ithaca, NY. Science, 2011; 333(6051): 1878-81.. Another study suggests the body’s clock is to blame for those tummy rumblings around dinnertime.

And while every person has a circadian rhythm, ladies tend to operate on fast forward— studies suggest their biological cycle is about six minutes shorter than men’s. Age is another important factor. It’s not just the appeal of the early bird special— changes in body clocks turn many older people into early risersAge-related decline in circadian output. Nakamura, T.J., Nakamura, W., Yamazaki, S., Kudo, T., Cutler, T., Colwell, C.S., Block, G.D. Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, California. Journal of Neuroscience 2011; 31(28): 10201-5.. And texting isn’t the only source of teens’ late-night habits: It turns out hormonal fluctuations may cause them to fall asleep and wake up later.

Circadian Rhythm ’n Blues — Your Action Plan

Disruptions in circadian rhythms can cause a range of health issues. Jet lag often results when people travel through time zones, since it takes a while for their body clocks to adjust. So someone who’s traveled from Madrid to New York might be ready to hit the hay at 5 pm, since their body thinks it’s almost midnight. For some, minimal daylight during the winter can bring on Seasonal Affective Disorder, a type of depression. Even the artificial light from computer and phone screens can throw the body clock out of whack, causing problems with sleep.

But no screwdrivers are necessary to repair a body clock gone haywire. Some solutions are pretty simple. Travelers can try popping a few melatonin pills, which research suggests can help ease symptoms of jet lagJet lag, circadian rhythm sleep disturbances, and depression: the role of melatonin and its analogs. Srinivasan, V., Singh, J., Pandi-Perumal, S.R., Brown, G.M., Spence, D.W., Cardinali, D.P. Advances in Therapy 2010; 27(11): 796-813..Medical professionals may also recommend bright light therapy to help treat a range of circadian rhythm disorders. For a few hours each day, the patient sits in front of a high intensity light that simulates sunlight. When circadian rhythms go offbeat, some also try behavior therapy, or modifying daily routines to get the cycle back on track. Sticking to a sleep-wake schedule, exercising during the day, and winding down before bed can help restore normal circadian rhythms. Now, learning to dance? That kind of rhythm’s a whole different story…