Circadian Rhythm: Its Function and Purpose in the Sleep/Wake Cycle

What is circadian rhythm?

If you’ve ever found yourself in another time zone after traveling with feelings of sleeplessness or exhaustion then you have suffered from what is commonly known as “jet-lag”. Jet-lag is a very real symptom caused by an interference with your circadian rhythm. On a cursory level, circadian rhythm is your body’s way of controlling when you should be asleep and when you should be awake.

Circadian rhythm, also known as your body clock, is mainly responsible for feelings of wakefulness. In some instances your circadian rhythm may be affected by outside influences. For instance, in the scenario where a traveler flies from New York to Paris overnight, David Randall explains the effect of jet-lag on your body clock, “when you land at eight o’clock in the morning Paris time, your body thinks that it is two o’clock in the morning [New York time]” (Randall 192). This is because your body was already working on the time set in New York, when you do something counter-intuitive (like travel from NY to Paris overnight) your body clock struggles to adjust and you operate as if you’ve been left behind (lagging) in NY, hence the term jet-lag. For many people the idea of a body clock never passes their mind, many people have a perfectly normal body clock and experience no issues whatsoever when it comes to mood and sleep. But for those who do suffer from sleep or mood disorders, circadian rhythm can be a big deal.

In her article “Times Of Our Lives”, Karen Wright says that one of the most common mood disorders, seasonal affective disorder (SAD), may be the result of the changing seasons messing with your body clock (Wright). Those who suffer from SAD experience depression-like symptoms in the winter months. The root cause of the circadian disruption comes from the changing day lengths, in the winter months people stick to their schedules which has them waking before sunrise which in turn leads to a very confused body clock. The solution may be simple, as Alfred J. Lewy, of Oregon’s Health and Science University says, “If we adjusted our daily schedules according to the seasons, we might not have seasonal depression” (qtd. in Wright). A common treatment for sufferers of SAD, in lieu of adjusting your schedule, is in the application of bright lights. Those with SAD may elect to sit in front of a bright light source for at least 30 minutes a day, thereby alleviating the symptoms of SAD by “tricking” their body clock.

The connection between circadian rhythm and depression does not stop there, a 2013 study published in the Proceedings of the National Academy of Sciences, points to a broader link between what is termed “major depressive disorder” (MDD) and “the disruption of circadian patterns” (Li et al. 9550) Jun Z. Li and his associates observed a number of genes related to circadian rhythm and found that in those with MDD there was a disruption in their circadian rhythm. Li and his associates explain that their findings could potentially lead to “the discovery of novel bio-markers” as well as more effective treatment for depression. (Li et al. 9554-9555). Novel bio-markers simply points to the discovery of new sets of genes that could be used in identifying depression in individuals. Through their work Li and his associates have effectively paved the way to better understanding the root cause of depression.

Although much can be said of circadian rhythm, very little is known of it’s newfound connection to depression. Your own circadian rhythm can be thought of as a physiological conductor of the orchestra that is your body. Without a focused conductor the orchestra becomes confused and eventually you have a cacophony of instruments all playing at once. Those who experience that cacophony, are those who suffer from mood disorders. Just as an orchestra relies on a conductor for coordination so too do you.