Circadian rhythm is the body’s “biological clock” that allows humans (and animals) to induce behavioral and physical changes while following a near twenty-four hour cycle. This cycle is a natural process that regulates our sleep and awake habits. The daytime exposure to light causes the clock to send messages that encourage wakefulness. As night falls, the biological clock starts to send signals that help keep us asleep throughout the night, increasing the manufacture of the hormone melatonin, which helps regulate sleep. By synchronizing our sleep and awareness with day and night, our circadian rhythm establishes a consistent schedule of restorative sleep that enables more daytime activity. The 24-hour natural cycle of the Earth is maintained, keeping the circadian rhythm in synchrony. Intake of food and degree of activity are two additional environmental cues that could synchronize the circadian rhythm. This procedure, however, is susceptible to several interruptions. Outcomes like jet-lag, daylight savings, and extreme shifts during work can sabotage our circadian rhythm. Thus leading to certain degrees of insomnia, narcolepsy, etc. Yet, with all this information on our sleeping/awake “clock”, is our circadian rhythm just a process to keep us in line and on a strict path of staying awake/asleep during hours, or is there something deeper below the surface?
Relating this back to a class speaker we had in November, Dr. Ravi Allada came to talk about sleep and circadian programming. In the article, “Circadian programming of the ellipsoid body sleep homeostat in Drosophila”, Dr. Allada and team experimented on planned brief lack of sleep in Drosophila at varying periods of the day and found that morning recovery was better than nighttime restoration (Andreani et al. 2022). The presynaptic protein BRUCHPILOT and the "clock" neurons, which tell us whether it is day or night, both showed levels of gene expression that were greater in the morning, which is consistent with clock circuit control. According to the time-dependent sleep rebound observed, the calcium levels in such cells rise in response to early sleep loss but not in the evening. These investigations provide information on the biochemical and circuit mechanisms that regulate a homeostatic slumber center through various circadian clock neurons. This study was eye opening in determining great ways to recover from lost sleep, and how we can manage/learn more about what occurs during sleep on a molecular level. Yet, it doesn’t tell us what happens when that lack of sleep adds up, and over time what neurological deficits will come into play.
To help supply some new insight on what negative disruption to our circadian rhythm can do to our mental and physical health, there was a scientific article published in 2020. In the article, “Circadian rhythm disruption and mental health” by Dr. Walker et al. brought up in the article how a number of mental diseases, such as major depression, bipolar disorder, anxiety, and schizophrenia, are associated with altered circadian rhythms. While disruption of circadian rhythms caused by jet lag, night shift work, or exposure to artificial light at night can cause or worsen affective symptoms in those who are susceptible, mood disorders are frequently linked to disrupted body clock timer responses, such as sleep and cortisol secretion. Strong correlations between the circadian system and mental health have been shown by research, but only recently have investigations into the direct connections between the sleep - wake cycle and mood regulation started. They concluded that, while rhythmic disruption cannot be the only factor contributing to mental illness, it may trigger or aggravate symptoms in people who are predisposed to mental health issues.
Tying in our speaker Dr. Allada from class, and from the article pulled with Dr. Walker et al., I found a news article titled, “Maintaining a daily rhythm is important for mental health, study suggests”, shedding light on what occurs to the human body when our circadian rhythm is out of its regular patterning. In the study, nearly 91,000 adults from the United Kingdom were examined for abnormalities in their daily sleep-wake cycles, or circadian rhythms (Lieber 2018). It utilized an accelerometer, a gadget worn on the wrist that records daily activity levels, to measure these interruptions. The study's findings showed that people with more circadian rhythm disturbances, which are characterized by increased engagement at night, reduced movement during the day, or both, were much more likely to exhibit symptoms of major depression or bipolar disorder. Based on a machine reaction time test, they were also significantly likely to have lower levels of wellbeing and lower cognitive performance (Lieber 2018). Even after adjusting for a number of determining factors, such as age, sex, lifestyle, education, and body mass index, the results remained consistent. Senior research partner, Dr. Doherty at the University of Oxford stated, “Previous studies have been very small, or relied on self-report measures. However, this study used objective device-based measures in over 90,000 participants; and then linked this information to standard measures of mood disorders, subjective well-being, and cognitive function.” Dr. Doherty brought up points of how this normal sleep study actually had amazing outcomes whilst looking into mental illnesses/disorders. Resulting in our circadian rhythm having more significance to us than we might have thought of before.
Overall, the topic of our circadian rhythm is relatively new to this century, and is ever evolving with new information to inform us about its world of benefits and its drawbacks. As college students, we can take this information and allow us to do better in school, and prepare for the real world, without having degradations to our mental health. The endless opportunities to dig deep into our sleep cycle have begun, and I cannot wait to see where we go from here.
Works Cited
Lieber, Mark. “Maintaining a Daily Rhythm Is Important for Mental Health, Study Suggests.” CNN, Cable News Network, 15 May 2018, https://www.cnn.com/2018/05/15/health/circadian-rhythm-mood-disorder-study.
Tomas Andreani, Clark Rosensweig, Shiju Sisobhan, Emmanuel Ogunlana, William Kath, Ravi Allada (2022) Circadian programming of the ellipsoid body sleep homeostat in Drosophila eLife 11:e74327
Walker, W.H., Walton, J.C., DeVries, A.C. et al. Circadian rhythm disruption and mental health. Transl Psychiatry 10, 28 (2020). https://doi.org/10.1038/s41398-020-0694-0
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