Circadian Rhythm Disorders: When Your Body Clock Doesn't Match Your Life

Your alarm clock and your body clock are not necessarily on the same schedule. A delayed circadian rhythm can shift both sleep and wake times later.

I remember these US Army ads from my childhood that used the tagline “We get more done before 9 AM than most people do all day.” These commercials placed a value on waking up early and being productive. And while some people’s biology really does favor an earlier start, this is far from universal. Others might barely be waking up at 9 AM but really come alive at night.

We tend to talk about sleep schedules like they're a matter of preference, discipline, or habit. Early risers are industrious. Night owls are slackers. If you aren’t going to bed early and waking up early, there is something wrong with you. I’m not sure where this societal attitude originated (we can probably blame the Puritans), but it’s reductive.

We all have an internal timing system called the circadian rhythm. This is a roughly 24-hour biological rhythm that determines the timing of sleep and wakefulness. We call your preferred sleep and wake times your chronotype. And there are early, intermediate, and late chronotypes.

Your Body Has a Clock—and It Doesn't Run on Willpower

There are two major processes regulating sleep: the sleep drive and the circadian rhythm.

Sleep drive, sometimes called Process S, determines how much sleep you get and the quality of that sleep. It’s homeostatic, just like eating. The longer you are awake, the hungrier you get for sleep. Once you fall asleep, you consume whatever drive you’ve built during the day until you wake up, at which point the process starts over.

The circadian rhythm, or Process C, determines the timing of sleep and wakefulness. The word “circadian” comes from Latin and means “about a day.” Your body temperature, melatonin production, and sleep-wake cycle are all on a circadian rhythm, which means it takes about 24 hours to complete a full cycle. All humans go through the same cycle, just at different times.

Infographic explaining the difference between feeling tired and feeling sleepy, including fatigue, sleepiness, and readiness to fall asleep.

When someone’s sleep is messed up, it could be due to a disruption to the sleep drive, circadian rhythm, or both.

Also, when working with a sleep issue, it’s useful to make a distinction between tired and sleepy. Sleepy means a high likelihood of falling asleep. Sleepiness is relieved by sleep. Tired is qualitatively different. Tired is fatigued, low energy, dragging ass. You can be tired without being sleepy. Tiredness is unlikely to be relieved by sleep. Instead, when tired, what helps is to take a break or move around.

For a more detailed look at the distinction between tired and sleepy, check out Difference Between Tired and Sleepy: Insight From a Sleep Therapist in Austin.

Sometimes people are not sleepy because they have not built up enough sleep drive yet, or something they are doing is working against their sleep drive.

For more about what impacts sleep drive, read Why Can’t I Turn My Brain Off At Night? and Want to Sleep Better? An Austin Sleep Specialist Says Spend Less Time in Bed.

And sometimes they are not sleepy because they are going to bed too early for their chronotype. For someone with delayed sleep phase, that's exactly what’s happening. Them going to bed at 10 PM is like someone else going to bed at 7 PM. Their circadian rhythm continues to promote wakefulness well into the window of time in which most people are sleeping.

How Does the Circadian Rhythm Actually Work?

Every known living thing on the face of the planet has a circadian rhythm, and every cell in your body has a circadian rhythm. Circadian rhythms are one of three types of biological rhythms in humans, the other two being infradian and ultradian. Rhythms are classified by how long it takes to complete one full cycle.

How does your brain know what time it is? Zeitgebers. Light is the most powerful timing cue, but your daily routines also give your circadian system information about when to be awake and when to sleep.

Infradian rhythms last longer than 24 hours. The menstrual cycle and hibernation are both infradian rhythms. Ultradian rhythms are shorter than 24 hours, usually 90 to 120 minutes. Human productivity tends to run on an ultradian rhythm, meaning we’re good for 1.5–2 hours of work before needing a break. And then there are circadian rhythms, which take about a day to complete. Sleep and wakefulness are on a circadian rhythm.

You have a master clock in your brain called the suprachiasmatic nucleus (SCN) that takes care of internal synchronization, or keeping all of your cells on the same schedule. But we also have external synchronization, or syncing up your body’s clock with the outside world, to contend with.

How does your brain know what time it is? Zeitgebers! Germans have words for everything, and this word means “time giver.” The most impactful zeitgeber is light. Depending on the timing of exposure, light can shift your internal clock earlier or later. Other zeitgebers include melatonin, meals, social interactions, and anything else you do at the same time every day.

I wrote an entire blog post about melatonin called Can Melatonin Help With Insomnia? Spoiler alert: no, but it can help with circadian rhythm issues.

Your Brain Starts Preparing for Sleep Before You Get Into Bed

Your brain starts preparing for sleep before you get into bed. With delayed sleep phase, melatonin production and sleepiness occur later—which is why “just go to bed earlier” isn't particularly useful advice.

I mentioned earlier that melatonin is a zeitgeber. Your melatonin production is on a circadian rhythm. We all have naturally occurring melatonin. It’s a hormone produced by the pineal gland in your brain at night. The purpose of this increased production is to convey to your SCN that darkness is settling in and sleep time should be coming within 1–2 hours.

We call the particular time your brain starts melatonin production your dim-light melatonin onset, or DLMO. The average DLMO is about 9 PM, which puts the average time of sleep onset around 11 PM. Some people have a DLMO of 10 PM or later. If your DLMO is happening after 10 PM, you are biologically still too alert to go to bed until after midnight.

This explains why “just go to bed earlier” is useless advice for some people. It’s like telling someone with a more conventional rhythm to go to bed at 7 PM. Ain’t no way they are falling asleep. Their DLMO hasn’t happened yet!

That's essentially what we ask someone with a delayed circadian rhythm to do when we tell them to get into bed at a “reasonable” bedtime. It’s not that they don’t want to fall asleep. They physiologically can’t.

Morning Larks, Night Owls, and Everyone in Between

Chronotype exists on a spectrum. Sleeping later than other people doesn't automatically mean something is wrong with your sleep.

Humans vary in their preferred sleep phases. The timing of when you sleep and when you wake up is partly determined by age and partly determined by genetics.

Let’s talk about age first. Our preferred sleep phases change throughout our lives. The rhythm consolidates over the first year of life. Naps are common in kids, but by the age of 10, sleep is happening in one long block. Teens will notice their sleep schedule shifts later and then shifts earlier again as they age out of adolescence. Older adults are usually on a pretty early schedule.

But genetics accounts for the rest of it. There are mutations in particular genes that predispose a person to be a lifelong night owl. These people tend to say they’ve always been this way, and the later schedule persists into older adulthood, when many of their peers are shifting earlier.

A typical adult sleeps roughly 11 PM–7 AM. This is an intermediate chronotype. People who tend to fall asleep and wake up earlier than that are called early or morning types, and people who fall asleep and wake up later than that are called late or evening types. Someone falling outside the norm doesn’t automatically mean there is a problem. It comes down to how your preferred sleep schedule interacts with your life.

When Does a Body Clock Become a Circadian Rhythm Disorder?

Some people build their lives around their chronotype. Morning types might take a job at a school or the morning shift at the hospital, and evening types might take a job at a restaurant or an evening or night shift at the hospital. This can work, and sometimes that’s what people opt to do.

Generally speaking, I see more problems arising in the late chronotypes than the early chronotypes. An early chronotype can make it difficult to have a social life, which is not nothing, but it’s not as impactful as a late chronotype that interferes with your ability to get to work or school.

Being a later chronotype isn’t bad on its own. If you are getting consistent, quality sleep, it’s fine if it happens later. But when there is a mismatch between how your body wants to sleep and the demands of your life, all kinds of problems can ensue.

This is where we start calling it a disorder.

What Are the Circadian Rhythm Sleep-Wake Disorders?

Someone with a circadian rhythm disorder has the ability to sleep, but at suboptimal times. There are a few different disorders in this category.

Delayed Sleep-Wake Phase Disorder

Delayed sleep-wake phase disorder (DSWPD), sometimes called delayed sleep phase disorder or delayed sleep phase syndrome, involves sleep and wake timing that occurs significantly later than conventional times. Importantly, the person sleeps well if allowed to set their own schedule.

For specifics, someone with delayed sleep phase will naturally fall asleep at 1 AM or later and naturally wake up at 9 AM or later. This is the circadian rhythm disorder I see most often in my practice.

To discern whether someone has a circadian phase delay, I ask the following questions:

If you had no responsibilities, what time do you think your body would prefer to go to sleep and wake up?

Do you sleep well if you can sleep on your preferred schedule?

This info, coupled with a few weeks of sleep logs, gives me my answer.

Advanced Sleep-Wake Phase Disorder

Advanced sleep-wake phase disorder is the same problem pushed in the other direction. Someone with advanced sleep phase falls asleep naturally between 6 PM and 9 PM and wakes up naturally between 2 AM and 5 AM. They feel alert and ready to go when they wake up and get sleepier as the day progresses. Like the delayed folks, they sleep well if they can sleep on their body’s preferred schedule.

There is less stigma attached to this sleep schedule, and the fallout is more related to social life rather than work or school. It’s rare to see this in someone besides an older adult.

Non-24-Hour Sleep-Wake Rhythm Disorder

In Non-24, we see a delay of the sleep phase by 1–2 hours each day. The sleep phase runs around the clock and will eventually come back around to where it was.

This shows up in people whose brains don’t respond to light, usually either due to blindness or brain injury. The human circadian rhythm is actually ever so slightly longer than 24 hours (the average is 24.3 hours), and morning light keeps us on a 24-hour schedule. All of us would see this type of movement around the clock if we were deprived of any light over a period of time.

Irregular Sleep-Wake Rhythm Disorder

Instead of having one consolidated nighttime sleep period, someone with irregular sleep-wake rhythm disorder has sleep and wake periods distributed irregularly across the 24-hour day. If you add the sleep periods together, they usually total 7-8 hours.

This is typically seen in cases of dementia, brain injury, cognitive impairment, or neurodevelopmental disorders.

Shift Work Disorder

Someone with shift work disorder likely has a conventional circadian rhythm. The problem is they are being asked to work a schedule that goes against their biology.

Not everyone who does shift work has shift work disorder, but if someone who works a shift that starts between 6 PM and 4 AM experiences excessive sleepiness while trying to work, difficulty sleeping when they need to sleep, or both, that warrants attention.

Circadian Rhythm Disorder or Insomnia?

Insomnia is an inability to sleep regardless of timing. A circadian rhythm disorder is an inability to sleep at times that work for your life.

They can both present as “I can’t sleep” or “it takes me forever to fall asleep.” But if the sleep problem resolves by sleeping at different times, that’s not insomnia.

But Here’s the Thing: You Can Have Both

Sleep disorders are fun. You can just collect them all if you want.

Sometimes insomnia develops on top of a circadian phase delay. Someone is unable to fall asleep at a time that allows them to get enough sleep. This creates problems in their life. They start worrying about it and taking a lot of measures to fix it. The sleep problem overtakes their life. Now we’ve got insomnia, too.

This is important to discern because insomnia must be treated before we address a phase delay.

How Are Circadian Rhythm Disorders Treated?

It’s about getting the right zeitgeber at the right time to stabilize or shift your circadian rhythm.

Depending on the disorder and the person, treatment can involve things like:

• Guidance around when to seek light and when to avoid light

• Stabilizing sleep and wake timing

• Adjusting the timing of daytime activities

• Strategically timed melatonin when appropriate

CBT for Insomnia is used to treat any insomnia that has developed on top of the circadian rhythm disorder, but it is not the primary treatment for the circadian rhythm disorder itself.

Sleep Hygiene Isn't Treatment

When you tell people, even some healthcare providers, that you can’t sleep, the advice you usually get is in the realm of sleep hygiene. Make your bedroom cold and dark. Watch caffeine intake. Put the screens away. None of this is bad. It’s just not treatment. It’s hygiene.

Brushing and flossing your teeth is hygiene. And it will prevent future problems. But if you have a cavity now, you need treatment. Hygiene won’t cut it. Sleep disorders need treatment, not hygiene.

I tell my clients to think of sleep hygiene as preventative care to put in place once their sleep is in a good place to keep it on track.

What About Sleeping Late on the Weekend?

A dramatically different weekend sleep schedule is basically a recurring time-zone change. Your brain starts adjusting to the new timing just in time for you to change it again.

You don’t have to have a full-on circadian rhythm disorder to have a dysregulated circadian rhythm. Do you ever sleep in on weekends or off-work days? Maybe you’re not getting enough sleep during the week, and you figure you can catch up now that you have time. Except now you’ve changed time zones.

You know how crappy you feel when you're jet-lagged? Malaise. Fatigue. Hungry at weird times. Tired at weird times. Wide awake at weird times. That's what happens when wake time is irregular throughout the week.

If your weekday and weekend schedules differ by several hours, you might as well be flying coast to coast every few days. Your brain is constantly adjusting to new time zones and never gets to land anywhere for long before you change it again. We call this social jet lag. Your brain loses its grasp on the time and doesn’t know if it should be awake or asleep.

Delayed types are particularly vulnerable to this because their weekday schedule may already be out of sync with their chronotype.

Your Sleep Schedule Isn't a Character Flaw

I have clients get told things like: “Dude, you're a grown-ass man. Go to bed!” People get side-eye from coworkers because they come into work later. Parents look at their phase-delayed teenager and see defiance and irresponsibility. We figure someone awake at 3 in the morning must be up to no good.

Being on a later schedule does often create problems in life. But it isn’t a moral failing. It’s biology. You’re struggling to wake up at 6 AM because, for your brain, it is the middle of the night. And even though this is your biology, there are things we can do to improve your life.

Circadian Rhythm Treatment in Austin

If you've spent years thinking, Why can't I just go to sleep like a normal person?, pay attention to what happens when you are able to sleep and wake as you please. Does your sleep improve? That might be a circadian rhythm issue rather than insomnia.

I provide delayed sleep phase treatment in Austin for adults whose internal sleep timing isn't lining up with the schedule they need or want to keep. Treatment focuses on understanding your actual sleep pattern and using behavioral interventions to help stabilize or shift it.

Your sleep schedule doesn’t have to wreck your life.