Our body is a well-set clock, which keeps good time, but if it be too much or indiscreetly tampered with, the alarm runs out before the hour.
Joseph Hall,
English bishop, satirist, and moralist
The human body is a masterfully engineered machine, sublimely tuned by nature. An estimated 37.2 trillion cells must work together cooperatively day and night. Have you ever stopped to wonder, How does this all work? or What keeps all these moving parts in order? Thanks to groundbreaking research, we have recently learned that every cell has its own timekeeper that can be thought of as a local clock. Deep within the brain, in the hypothalamus, lies a master clock that regulates all the local clocks, making sure that each one is set to the same time. This complex, coordinated process is in sync with the alternating cycles of day and night and with all the degrees of changing light that occur in a twenty-four-hour period as Earth rotates on its axis. Called the “circadian rhythm”—from the Latin words circa, which means going around, and diem, meaning day—this internal process regulates the human body’s sleep-wake cycle, among many other functions.
The master clock (think of it as circadian rhythm central) sends hormonal and nerve signals throughout the body, synchronizing the cells’ clocks to the day-night, light-dark cycle of life. On a continuous basis, the master clock can determine what time it is based on messages from photoreceptor cells in the retina that register light conditions outside and report these to the brain via specialized pathways.
Meanwhile, the cellular clocks keep local time, making sure that various activities locally are timed right and are appropriately coordinated with other cells and organs. This is why, for example, key enzymes are produced at certain times, blood pressure and body temperature are controlled, hormones are secreted, the gut microbiome is populated with the right balance of bacteria, and gut motility is appropriate for the hour. Satchin Panda, PhD, a professor in the Regulatory Biology Laboratory at the Salk Institute for Biological Studies in La Jolla, California, and author of The Circadian Code, notes that these specialized circadian clocks help “every cell figure out when to use energy, when to rest, when to repair DNA or replicate DNA.” Working in harmony, these internally synchronized pacemakers help maintain homeostasis, the body’s physiological equilibrium, to ensure proper functioning and good health.
Occasional interruptions to your body’s inherent time-keeping systems—from traveling through a few time zones, for instance—aren’t a big deal. But as Dr. Panda explains, “Repeatedly disrupting your circadian clock can have adverse health consequences, as every system in your body starts to malfunction.” The regulatory scheme of our innate circadian rhythm does the equivalent of “knocking” on every cellular door to communicate, at any given moment, what time it is and what it should be doing. Because it regulates the release of essential hormones, including cortisol (the primary stress hormone), melatonin (which sets the stage for sleep), and serotonin (a feel-good neurotransmitter), the body’s circadian rhythm governs your sleep, blood pressure, pain response, allergic response, digestive function, immune response, mood, alertness, energy, and even the way you metabolize medications. If you’re disturbing your circadian rhythms and their entrainment (or synchronization), it’s tantamount to believing you can drive to an unknown place without using a GPS or even a map while having random obstacles thrown in your path and still expecting to arrive at your destination safely and in a timely fashion. It’s not gonna happen.
If you don’t travel often or stay out late on weekends, you might think you don’t need to be concerned about this issue. But that’s not true. Every day, many of us are living and working in ways that are at odds with our physiology, compromising the timing and functioning of our internal body clocks. Many of us are living with serious disruptions to our circadian rhythms, because we’re exposed during the evening hours to too much bright, indoor light and excessive additional light from technological devices. These choices, made unwittingly, lead to the loss of precious downtime and in some cases to essential time to reset our psyches in thoughtful reflection or even the opportunity to experience awe or wonder (more on that later). What’s more, these days, people often have inconsistent sleep habits—sometimes wildly inconsistent ones—that throw their body clocks further off course. As a result, we end up forcing our bodies and minds to work harder or less efficiently than they need to, which has ripple effects on our whole system.
Here’s one way this can happen: On a typical weekend, people often stay up later than usual, then sleep in past their regular wake-up times, throwing their bodies’ internal clocks off even more than they were during the week. Meanwhile, spending weekday evenings exposed to bright lights and to the intense blue light from digital devices resets their internal clocks because it fools the light-sensitive cells in the eye into believing that it’s still daytime. This then suppresses the release of the sleep-inducing hormone melatonin, making it even harder to fall asleep. Whether it’s because of this delay in melatonin release or the shortened night of sleep the person gets, melatonin (nicknamed the “hormone of darkness”) can stay elevated for several hours in the morning—part of the reason people often feel groggy, foggy, and cranky during the day, especially during the week.
One of my patients, thirty-six-year-old Sean, is a social worker and an aspiring songwriter who lives with his girlfriend. Because he has a demanding day job, he often stays up late to work on his music. Once his creative juices start flowing, he’s able to write lyrics and put melodies to them for hours at a time, as he enters a state of “flow,” or complete immersion. Coined by the psychologist Mihály Csíkszentmihályi, the term flow describes an optimal state of complete absorption with what you’re doing that can cause you to lose all sense of time and space. It’s an incredibly gratifying experience while you’re in it, as Sean well knows. But because he was getting so stimulated by his own creativity at night and skimping on sleep as a result, he would end up feeling agitated and on edge during the day. Needless to say, this is not a good state for a social worker to be in.
Besides being sleep-deprived and emotionally revved up, the real problem Sean was grappling with was a massive case of social jet lag. Social jet lag was coined in 2006 by Till Roenneberg, a professor of chronobiology at the Institute of Medical Psychology at Ludwig-Maximilian University in Munich, Germany, to describe the misalignment between a person’s social and biological time-related needs—that is, the gap between how we are living and what our bodies call for at any given time. It has become an incredibly common hazard of modern life. Unlike the jet lag you might experience from traveling across various time zones, which is transient until your master clock recalibrates to the local time, social jet lag doesn’t require you to leave home. Worse, it can become chronic: The phenomenon occurs when there’s a conflict between what your body needs, based on your personal sleep quota and the timing of your internal biological clock—whether you’re an early riser or a night owl, for instance—and what your life requires, based on your job, your family responsibilities, and other factors.
In an illuminating study, researchers from the University of Chicago conducted a two-year analysis of the activity patterns of 246,000 Twitter users throughout the US to reveal how technology and social pressures are taking a toll on our sleep habits and our daytime functionality. By monitoring and analyzing Twitter activity in fifteen-minute increments, the researchers discovered that continuous periods of low Twitter activity were linked with adequate sleep but the nighttime break in tweets shifted to later times on the weekends than on weekdays. They found that people in the US experience an average of seventy-five minutes of social jet lag from weekdays to weekends, with those in the Central and Eastern regions of the US having a greater amount than those in the West. The magnitude of social jet lag also varies by season, with less occurring in the summer.
Previously, in a large-scale, epidemiological study, researchers from Germany and the Netherlands analyzed the sleep duration, sleep timing, and social jet lag among 65,000 people living in Europe. It turns out that 69 percent of them suffered from social jet lag, experiencing at least a one-hour difference between how long they slept on weekdays versus weekends, and one-third experienced a two-hour discrepancy or more. This suggests that people’s circadian rhythms are continuously being forced to adjust and readjust to shifting social pressures. The researchers also found that in recent years the amount of time people spend outside absorbing light has declined dramatically, and that those with social jet lag have a higher likelihood of being overweight.
This isn’t surprising given that scientific research has found a correlation between insufficient sleep, levels of appetite-regulating hormones, and increased food consumption. Specifically, too little sleep leads to an increase in the hormone that makes us feel hungry (ghrelin); at the same time, too little sleep leads to a decrease in the hormone that signals when we’ve had enough to eat (leptin). It doesn’t take a math whiz to run the equation: alterations in appetite-regulating hormones—particularly, elevated levels of ghrelin and decreased levels of leptin—add up to increased food consumption. In addition, social jet lag can have serious metabolic consequences, significantly increasing a person’s risk of developing metabolic syndrome (a dangerous cluster of conditions that includes elevated blood pressure, high blood sugar, excess belly fat, and high cholesterol or triglyceride levels), prediabetes, or type 2 diabetes, especially in adults. Unseen by the naked eye, metabolic syndrome causes the entire body to be prone to inflammation, increasing the risk of heart disease, stroke, and type 2 diabetes.
Not surprisingly, social jet lag tends to go hand in hand with insufficient sleep, which is a problem on its own. But social jet lag also involves being active and awake when you should be sleeping, or snoozing when you should be alert and engaged, either of which can throw your body and mind into states of disorientation and disequilibrium. These circadian rhythm disruptions are a large part of the problematic dynamic linking shift work with an increased risk of developing multiple medical conditions, including breast and prostate cancer, gastrointestinal disorders, cardiovascular disease, and diabetes.
But even if you work a nine-to-five schedule, you can still set yourself up for social jet lag, and it can have a substantial spillover effect on the rest of your life. Indeed, the effects can be far-reaching, contributing to problems with excessive daytime sleepiness, compromised academic achievement, impaired cognitive function, and even challenges with controlling one’s balance. Moreover, social jet lag can have a detrimental impact on your mood and state of mind, potentially leading to emotional distress, including anxiety, depression, and aggression, as well as unhealthy behaviors such as increased alcohol consumption, bad eating patterns, and decreased physical activity. A study from Maynooth University in Ireland even found that social jet lag in adults is associated with attention deficit symptoms and impulsivity. In other words, social jet lag can amplify many different forms of emotional inflammation, fueling agitation, depression, manic behavior, impulsivity, and other unwanted states of mind—without you even realizing it.
Jennifer, a forty-nine-year-old humanitarian aid worker who often traveled to war-torn countries and sites that had been ravaged by natural disasters, discovered this the painful way. Her work involved long hours, extensive air travel, occasional brushes with danger, and lots of time away from her husband and three teenagers. Calm, compassionate, and measured by nature, Jennifer made it all look easy, but the suffering she saw and the tragic stories she heard took a toll on her. By her own admission, she drank too much wine, didn’t get enough sleep, and had developed an exercise addiction (to running, in particular, which she called “my form of Prozac”).
After a three-day trip to Syria left her severely sleep-deprived, and her flight home was delayed by six hours, Jennifer arrived home feeling frayed at the edges. When her husband vocalized his resentment about her extensive work travel and her distractedness when she was home, she became uncharacteristically irritable with him. It had become an ongoing refrain in their marriage, and it didn’t usually bother Jennifer. But after this trip she became more reactive toward him.
She hadn’t recovered her equanimity before heading off on another work trip forty hours later. After that, the cycle of social jet lag (compounded by travel jet lag) began anew, and it persisted. Somehow Jennifer continued to manage the stress of dealing with the suffering she saw, and she remained poised and proficient at work. But when her mercurial schedule and extensive travel disrupted her internal equilibrium, she reached a tipping point and became alternately combative or withdrawn from her husband—reaction styles that felt foreign and quite uncomfortable for her and, of course, for her husband.
To try to counteract the undesirable symptoms of social jet lag and emotional inflammation, people are increasingly seeking medications—stimulants to pep them up and help them focus during the day and/or drugs to help them relieve anxiety or snooze better at night. Between 2006 and 2016, the use of prescription stimulants doubled in the US. The use of antidepressants has increased 65 percent since 2000. And from 2014 to 2018, the use of benzodiazepines (commonly known as “tranquilizers”) more than doubled among adults in the US. These trends address the wrong issue because they are not getting to the source of the problem, and they bring on another set of problems because many of these drugs foster tolerance and dependence. Plus, their use creates an unhealthy feedback loop in which people take desperate measures to try to correct their own self-sabotaging behaviors, hoping for a better outcome, but they are really just hitting the repeat button on the harmful cycle.
What they should be doing instead is taking steps to restore their bodies’ natural rhythms. A case in point: Researchers at the University of Colorado Boulder found that when healthy people went camping in nature for just one weekend during the summer, melatonin was released one-and-a-half hours earlier, and peak melatonin levels occurred an hour earlier during the night. These hormonal shifts help people fall asleep more easily, maintain sounder sleep throughout the night, and wake up more easily and naturally. In other words, going camping can counteract the negative effects of our modern lifestyle and essentially reset our bodies’ circadian rhythms, thus preventing social jet lag.
City dwellers, take heart: You don’t need to head into the woods to reap these benefits. These effects have nothing to do with sleeping in a tent and everything to do with the fact that while camping, you’re not looking at brightly lit devices at night or going to bed at random times. Instead, you’re going to bed shortly after it gets dark and you’re waking up with the sun. Spending daytime hours in natural sunlight—which provides more than four times the illumination you’d experience inside during the summer—also contributes to better sleep patterns and daytime alertness. All of these beneficial patterns can be achieved wherever you are if you dim the lights when the sun goes down and wake up shortly after the sun rises and expose yourself to natural sunlight, whether you’re sleeping in nature, the suburbs, or right in the middle of the city.
In a small study at the National Institute of Mental Health, a group of volunteers was followed to see the effects of artificial light on their sleep patterns. They were in complete darkness for fourteen hours at night (compared to their usual eight hours in the dark), with no exposure to artificial light. In just three weeks their sleep settled into different patterns—often segments of four to five hours at a time—but perhaps more significantly their nighttime secretion of melatonin increased, and they logged an additional hour of sleep during the night. In the debrief that followed, participants reported they had never felt so awake and spoke of experiencing “crystal clear consciousness.” When I spoke to my friend and colleague Tom Wehr, MD, about his study, he asked, in a pain-tinged voice, Is being fully awake something that most people in modern society will never know?
Research from the University of Geneva in Switzerland found that imposing a curfew on the use of electronic screen devices at 9:00 p.m. in the evening improves the early onset of sleep, increases sleep duration, and enhances daytime alertness. There’s no mystery to the mechanism behind this effect: Using electronic devices (tablets, laptops, smartphones, and even TVs) before turning in for the night suppresses the release of the sleep-promoting hormone melatonin, thanks largely to the artificial blue light that is emitted by these screens. Normally, the pea-size pineal gland in the brain begins to release melatonin about two hours before your usual bedtime. Exposure to any bright light in the evenings can prevent the pineal gland from releasing melatonin, thus delaying sleepiness. But blue light is especially problematic, because it is highly activating. Even if you’re not staring at a screen, if enough blue light strikes the eye, melatonin won’t be released at the appropriate time, and it will be harder to get in the mood to snooze. And if you slip into bed with your laptop, phone, or tablet, as many people do these days, you’re asking for trouble: the more electronic devices you use in the evening, the harder it becomes to fall asleep or sleep soundly.
Teens are particularly vulnerable to these effects because their circadian rhythms shift a bit later at night naturally during adolescence. So watching TV, FaceTiming with their friends, or playing video games will delay the release of the sleep-inducing hormone even later, which will make it more difficult for them to get up on time for school.
Let’s face it: We live in a 24/7 world that rarely unplugs or turns off completely, where the pings, dings, buzzes, and ring tones that emanate from our digital devices have become the soundtrack of our lives. This can have an insidious effect on our minds and bodies, partly due to technostress—the vigilance of being on guard and having to respond to whatever request comes next—but also due to the stimulating effects light-emitting devices have on our brains.
And thanks to our cubicle culture, many of us are deprived of sufficient natural light during the day, which saps our vitality, interferes with our ability to focus, and compromises our productivity and our moods. Making matters worse, inconsistent sleep-wake patterns—alternating between sleeping too little and too much, along with bedtimes and awakening times that are all over the map—further disrupt our internal clocks. Like rowdy teenagers throwing a party when their parents are out of town, we are breaking the rules and failing to realize there will be consequences. But there are. Our bodies register the effects of stress and chaotic schedules, and they register the disregard for the harmonious rhythms our bodies have evolved to need.
We’re not masters of the universe the way we may like to think we are. The advent of technology has given us this false sense of mastery, lulling us into thinking that we can work anytime, anywhere, or have the lights on at any time of night without suffering negative consequences, despite the fact that for millions of years, plants, animals, and other living things have been living in sync with the light-dark cycles of the universe. Until artificial lighting was developed, the sun was the primary source of illumination for human beings, and after sunset, people settled down into the fading light.
As a result, they usually got plenty of rest or sleep. Fortunately, you can flip the switch on these habits by respecting your circadian rhythms. Honoring your body’s natural rhythms is a crucial first step toward maintaining your physical and emotional equilibrium. The body is a bit like a Rubik’s Cube: When the parts (or systems) are in the proper alignment, changing one thing can send everything else off-kilter; the more things you change, the more difficult it is for your body to achieve alignment because of the cascade of effects on other systems. Some people are better at compensating for these disruptions to their body’s equilibrium than others, but many of us are left struggling.
On the other hand, living in harmony with the way we have evolved brings physiological and emotional balance, creating a good fit between our bodies and minds, between what we’re doing and how we’re designed to function. Honoring our body’s natural rhythms helps stabilize our mood, become more resistant to stress, feel less physical pain, and generally feel and function better physically and mentally. It’s an essential step in cooling and calming emotional inflammation.
The following are some ways you can adjust your habits so that they support your body’s inherent rhythms:
The question of how to go to bed earlier when you’re not used to doing so is a bit of a conundrum. If your bedtime has been inconsistent and you want to start turning in at 10:00 p.m., you may not feel sleepy initially. One strategy that sleep experts sometimes recommend is to move your bedtime fifteen to thirty minutes earlier each week until you’re consistently getting the amount of sleep that makes you feel and function at your best in a time frame that works for your life. That’s what Sean, the social worker, did. At my suggestion, he gave himself a creative curfew of 11:00 p.m. for his songwriting and gradually worked himself into a consistent sleep schedule. Once he was getting enough sleep regularly and he had recovered from his social jet lag, his daytime moods became steadier, and he found it easier to handle the emotional vicissitudes he regularly encounters working with his clients.
Consider talking to the powers that be at work about the quality of the artificial lighting in your office because it will affect how you feel and function, too. If you crave the warm, cozy glow of incandescent light bulbs, a “soft white” LED bulb labeled “2700K” is soothing. In commercial spaces where bright light is called for, “bright white” or “cool white” bulbs (3500K–4100K) or “daylight” bulbs (5000K–6500K) are used because they are associated with increased productivity and alertness and are generally energizing. The highest numbers include blue tones, which are especially activating and can enhance vigilance, reaction times, and faster cognitive function. Fluorescent lights, by contrast, can have a negative impact on mood and lead to eyestrain and dizziness in some people, whereas some studies show that exposure to red light can increase alertness and performance in the afternoon. So consider the quality and type of your artificial indoor lighting carefully.
Keep in mind that a wide array of prescription and over-the-counter medications, including certain antidepressants, decongestants, anticonvulsants, bronchodilators, corticosteroids, beta-blockers, and anticholinergic drugs, can contribute to sleep problems. Even ibuprofen and aspirin have been found to disrupt sleep in some people, increasing the number of awakenings and decreasing their sleep efficiency. If you suspect a particular medication is making it difficult for you to fall asleep or is causing middle-of-the-night awakenings, talk to your doctor to see if perhaps you can change the time of day when you take it or find a substitute drug.
Similarly, eating heavy, fatty, or spicy foods in the evening can cause sleep problems for some people. Pay attention to your caffeine intake as well, not just from coffee but also from tea, chocolate, and coffee-flavored foods (such as ice cream or yogurt). In some people, caffeine is metabolized very slowly, and it can take their bodies as long as nine to twelve hours to completely remove it from their systems. If this describes you, having a pick-me-up latte at 3:00 p.m. could end up leaving you wide awake at 10:00 p.m. when you want to turn in for the night.
Ultimately, honoring your body’s natural rhythms requires taking back control of your nights and days. It’s about putting time on your side and making conscious choices about the way you want to live so that you can restore your internal equilibrium, physiologically and psychologically.
Yes, changing your behavior requires giving up the patterns you chose, consciously or not, in the past, and making the switch does take some effort and resolve. But if you make it a priority to stop upsetting your body’s internal rhythms and start living in sync with your body’s inherent needs, the payoffs will be well worth the effort. Your mood is likely to end up on a more even keel, and your energy will increase. Your physical health will probably improve and your emotional equilibrium will, too. Think of it this way: By respecting your body’s rhythms and doing whatever you can to maintain their regularity, you’ll be resetting your internal emotional thermostat, which will improve the way you react to and deal with the stresses and strains that are unavoidable in our modern world.