Body Clocks + Biorhythms: Immunity, Mood, and Well-Being

A few weeks ago, I did a post on Seasonal Affective Disorder that advised exposure to light early in the day (within two hours of waking) and recommended other practices. That post lacked context, and prompted the apology post you’ll see after it. At the time, I promised to provide that context. Here it is.

Almost all species have internal rhythms and a sense of time, which are the focus of a field now known as chronobiology. We have internal circadian (24-hour) clocks that generate and shape daily cycles in our physiology, emotion, and behavior. 

Most organisms inherit the ability to track time on this 24-hour scale. For example, bees use their clocks to visit flowers at the appropriate time of day so they can feed when flowers are open. Birds use their biological clocks during migration to compensate for the changing position of the sun throughout the day. Other mammals rely on them to forage at the ideal times for avoiding predation. 

We can “see” and appreciate sunlight consciously using visual perception, such as watching the sun rise in the morning. Yet light has another aspect distinct from conscious visual perception. In this aspect, it influences myriad bodily functions, particularly your circadian clock. 

The term “circadian” comes from the word circa, meaning “approximate,” and diem, meaning “day”–so, approximate day. Without contextual information from the outer world, you have a daily rhythm that is closer to 24.2 hours. Getting sunlight adjusts your behavior to a solar day; otherwise, your rhythm would be off–in just five days, for example, you’d be off by a full hour. In one month, you’d be off a full six hours. The effects of being out of sync show up at the level of the cell, the tissue, and behavior.

Your circadian clock is always trying to figure out “when” we are in time–and along with it, how to be in the (cellular) moment! To be in synchrony with the solar cycle ensures our health and our survival. 

For our clocks to provide evolutionary benefit, they must be continually tuned, like any other instrument, to ensure that they’re in harmony with external time. This is called circadian photo-entrainment; it happens below the surface of conscious awareness. And it happens thanks in large part to a newly-discovered (in 2002) set of photoreceptors in your retina that relay light information to the areas in the brain that house the circadian rhythm-maker that tunes all the clocks in our bodies to the light-dark cycle. 

The development of artificial lighting and the demands of capitalism (among them, the pressure to be productive much later into the night) mean that our light exposure has increasingly diverged from the natural day + light cycles. This has consequences: A recent research study shows that adolescents with greater levels of nighttime light had a higher prevalence of mood and anxiety disorders. This happens to adults, also. 

As we’ve come to note in myriad settings, capitalism (particularly, racial capitalism) doesn’t just trigger the initial harm, the out-of-syncness with natural light and rhythms and the natural world around us. Marginalized folks, and those more likely to be impacted by the negative effects of climate change, food apartheid, and other forms of oppression are also less likely to be given standard daytime work shifts and more likely to work jobs that do not comply with national legal requirements for breaks. 

When we are not able to sync with our circadian clock, to live in tempo with the rhythms of our light-dark cycles, the health effects include disruptions in sleep, disturbances in mood, chronic inflammatory disease, and multiple impacts on learning and memory. Here again, we can see how capitalism, racial capitalism, and so many other forms of oppression intersect to affect health and well-being.

For the optimal interchange of sleep + wake rhythms, researchers recommend getting light outside early in the morning and, if possible, not through windows. If you do it daily and are pretty regular with it, 5-15 minutes of “fresh” light should be sufficient. These exposures to light in the morning also prime the evening release of natural melatonin that supports healthy sleep. Exposure to light in the afternoon, and then as the sun is setting, is also considered helpful in addition to tune the circadian clock and prime healthy sleep. This can include walking around the block, walking to the bus, stepping outside work to take a 5-minute break, and any ingenious ideas you have when you work for companies that dictate your hours, and when you have children and family members to care for.

Basic health and unity with the rhythms of the natural world should be a birthright and not a privilege. Yet like so many other body rights, they are given to people with multiple nodes of privilege. I offer this information and the social context behind it to highlight that it belongs to our basic health and well-being, rather than the wellness industrial complex version of health. This is why yoga, psychotherapy, and wellness are inherently social + political, and why honest dialogue about these and other rights is critical.

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