Rest assured when you know your internal body clock

What is an internal body clock and circadian rhythm?

The idea that we have an internal body clock was first noticed in the 18th

century by French scientist Jean-Jacques d’Ortous de Mairan who noticed that plants

that kept steady temperatures in a dark space also continued their

daily rhythm of opening and closing their leaves. De Mairan thought that this was because

the plants could “sense the sun without ever seeing it”(1). – The term

“circadian” comes from the Latin words “circa” which means “about” and

“diem” (day)– together they mean “about a day”.  The term was first described by

Romanian biologist Franz Halberg in 1959 who found that circadian rhythms are in part,

endogenous, meaning they work internally) and they can be manipulated by

outside factors, such as the influence of light.   Circadian rhythms

which are present in humans, plants, animals and marine life, help regulate the body to

attune with different parts of the day. Changes in length of daylight inform

the body what to do.

In an article about circadian rhythm, neuroscientist,

Louis Ptacek, MD, Professor of neurodegenerative diseases, UCSF

Weill Institute for Neurosciences describes how light and darkness control our

internal body clock, and he explains it as “the 24-hour cycle of

waking and sleeping in response to daylight and darkness. When you’re

sleeping and the sun comes up, your eyes sense the light even when

they’re closed. That light sends a signal to the master clock in your brain

signaling you to wake up.” Your body gets ready for the day by raising its temperature

blood pressure and helps awaken your digestive tract and immune

system to become more active.  With the darkness at night the body knows

to reverse this process.” [2}] 

How does this happen? 

Research into the science of circadian rhythm and internal body clock is explained

by the ways in which a cluster of approximately 20,000 cells in our brains, called the

suprichiasmatic nucleus cells, (SCN) regulate the different

biological roles in our bodies, including our sleep and wake cycles, our

metabolism and digestion. Interestingly, environmental

factors, such as light have one of the most powerful effects on our

circadian rhythms. Light is taken in by the retina of the eye and then cells

send information to the pineal gland and other parts of the brain telling it to stop

producing the hormone, melatonin, which plays a key role in helping us to sleep.

(3)

How Disruption to Circadian rhythm causes problems with sleep

When your body’s internal clock is disrupted, your body’s natural rhythm

(circadian rhythm) is thrown off balance. potentially causing a variety of difficulties,

including  short-term effects like problems sleeping, fatigue, and trouble concentrating,

as well as longer-term health issues such as weight gain, and more serious

conditions, including mood disorders. 

In addition, we know that light, and lack of light especially in the Fall and

Winter months can cause a variety of mood difficulties and

depressive symptoms, including Seasonal Affective Disorder (SAD).  

Importantly, it is thought that a major component that triggers all

mood disorders, including SAD, major depressive disorder (MDD),

and bipolar disorder (BD) are partly triggered by disruptions to the sleep and

wake cycle [4]

Because of this, prioritizing sleep is paramount for good self care

and it’s especially important during the Fall and Winter months

when we turn the clocks back and get less natural light.  Karin Johnson,

a neurobiology professor at the University of Massachusetts

Chan School of Medicine and a member of the American Sleep Medicine Advocacy

Committee states that when we pay attention and sync our activities to align with

the sunrise and sunset, we will have better quality of sleep as well.

This view aligns with those of the AmericanAcademy of Sleep

Medicine (AASM), American Academy of Neurobiology

and the health and safety-focused non-profit, National Safety Council.   

Ways to naturally optimize your sleep and support your internal body clock

—Get morning light.

—Avoid blue light from screens, especially at night.

—Exercise, but not too close to your bed time.

—Try to eat meals at consistent times each day.

and not too late at night, if possible.

—Limit caffeine and all substances that can impede sleep.

—There is much on the topic of nutrition, but eating a nutrient dense

diet, reducing sugar and processed foods will go a long way to supporting your

body’s natural internal rhythm. (5)

Seek help from a healthcare practioner and consider behavioral therapy

If your mind is racing at night, or if you are suffering from anxiety and/or depression

it can be extremely difficult to relax enough to get a good night of sleep. Menopause,

and other hormonal shifts can also contribute to low mood and lack of good quality sleep.

Working with your health care provider to identify any physical barriers to sleep is

key, as well as working with your mental health provider to address emotional

symptoms of anxiety, depression, and any trauma-related symptoms.

According to the Mayo Clinic, sufferers with insomnia can be effectively

treated with behavioral therapy (6). The study cites cognitive behavioral therapy

as a way to treat long term sleep problems and is the first line of recommended treatment.

Other types of treatment such as internal family systems therapy,

often referred to as parts work is another model that may prove to be beneficial.

Through a collaborative approach this model helps you to identify parts,

thoughts, or feelings that can disturb sleep.For example, you could have

anxious parts that stay up and try to process your fears and worries at night,

a depressed part that may sleep too much during the day so

that sleeping at night becomes difficult. Or even productive parts

that want you to keep working when it would be better off if you slowed down.

If you are having trouble with any of these parts or if you would like help with working

toward improved mental health, working with a therapist is time well spent and could

help you to tune into your internal system, teach you to ways to optimize and understand

your unique circadian rhythm leading to greater emotional and physical well being.

1) The birth of chronobiology: a botanical observation.

by Jonathan Sobel, PhD | Sep 23, 2019 | Clocks in the Spotlight

[2] Why Is It So Hard to Adjust When Clocks ‘Fall Back’? |

UC San Francisco. (2025, October 30)https://www.ucs

f.edu/news/2025/10/431001/why-it-so-hard-adjust-when-clocks-fall-back

[3] What Is Circadian Rhythm? (n.d.). Cleveland Clinic. Retrieved November 9,

2025, from https://my.clevelandclinic.org/health/articles/circadian-rhythm

[4)
Dollish, Hannah K., Mariya Tsyglakova, and Colleen A. McClung.  Circadian]

Rhythms and Mood Disorders: Time to See the Light.”

Neuron 112, no. 1 (2024): 25–40. https://doi.org/10.1016/j.neuron.2023.09.023

.

[5] Circadian Rhythm Disorders: Treatment

https://www.nhlbi.nih.gov/health/circadian-rhythm-disorders/treatment

[6] Insomnia treatment: Cognitive behavioral therapy

instead of sleeping pills. https://www.mayoclinic.org/dis