If Cassidy Sokolis ever needs to wake up before 11 am, she scatters three alarm clocks throughout her bedroom. Even then, she still often sleeps through the clamor.

"It's really frustrating," Sokolis, a 21-year-old junior at Northern Arizona University, tells me. "People have mocked me for it, saying how lazy I am, that I'm not trying hard enough. That really bothers me. Because it's my brain's fault, not mine."

A college student would say that. But her doctors say it isn't just an excuse.

When she was 19, Sokolis was diagnosed with delayed sleep phase, a disorder that sets her internal clock permanently out of sync with the rest of the world. It's not that she needs more sleep than the average person. It's just that her body prefers her to begin a seven- or eight-hour cycle after 3 am.

While she's still a college student, Sokolis can start her day at 11 am, thanks to a flexible class schedule. But now she's nearing graduation, and she's worried her unusual schedule will get in the way of her dream of becoming a teacher — a profession with notoriously early start times. "If it's between changing my career and finding a way to make it work, I'm definitely going to have to find a way to make it work," she says.

Sokolis is on the far end of the bell curve of human sleep habits.

We all have a preferred, inborn time for sleeping. Science has validated the idea that there are "morning people," "evening people," and those in between. These are called chronotypes. And just like it’s rare for a person to be 7 feet tall, it’s rare for Sokolis to not be able to sleep until 3 am. We all have a chronotype, just like we all have a height.

Even people who are slightly more oriented to the evening — people who would like to sleep between 1 am and 9 am, say — may be faced with a difficult choice: Listen to your body, or force it to match the sleep habits of most everyone else?

Research has been gaining insight on that question. It turns out our internal clocks are influenced by genes and are incredibly difficult to change. If you're just not a morning person, it's likely you'll never be, at least until the effects of aging kick in.

And what's more, if we try to live out of sync with these clocks, our health likely suffers. The mismatch between internal time and real-world time has been linked to heart disease, obesity, and depression.

This all amounts to a case — not an absolute case, but a compelling one nonetheless — that we should listen to our bodies and not the alarm clocks.

Your body is a clock

Most people — around 30 to 50 percent — fall right in the middle of the chronotype bell curve, sleeping between the hours of 11 pm and 7 am.

Another 40 percent are either slightly morning people or slightly evening people, off by an hour or so.

People like Sokolis are even more rare: Only around 0.2 percent — one out of 500 — of adults have a delayed sleep phase like Sokolis. (The condition is much more common among teens, whose clocks gradually shift earlier as they age.) A few more adults (1 percent) have advanced sleep phase syndrome and prefer to go to sleep around 8 pm, according to the American Sleep Association. Society tends to be more forgiving of them.

To understand why some people are early birds while others are night owls, let's consider the body's circadian system. The body is an orchestra of organs, each providing an essential function. In this metaphor, the circadian rhythm is the conductor. (Listen to this NPR story for a cool musical version of it.)

The most important thing to know about the circadian system is that it doesn't just control when we're sleepy. "Every neurotransmitter, hormone, and chemical in the body cycles with the daily rhythm," Philip Gehrman, a sleep researcher and clinician at the University of Pennsylvania, tells me. "It’s not just humans; even single-cell organisms follow a circadian rhythm. It really seems to be a fundamental property of life."

Our bodies run this tight schedule to try to keep up with our actions. Since we usually eat a meal after waking up, we produce the most insulin in the morning. We're primed to metabolize breakfast before even taking a bite. It's more efficient that way.

For people who are either more morning-oriented or evening-oriented, everything the circadian system controls is delayed.

"Evening types on average get down to their lowest core body temperature later than normal," Leon Lack, who studies circadian rhythms at Flinders University in Australia, tells me in an email. "Their circadian system doesn’t start producing sleepiness until later or alertness until later." They also release cortisol, the stress hormone, later than average. Most people hit their peak alertness around 10 am. Evening-type people can hit theirs hours later.

Some extreme night owls gather on Reddit to discuss the unique challenges of being out of sync with the world. That's where I found Sokolis and several others, including Kat Park, who were willing to share their personal stories. Mainly I wanted to know what it feels like to be on a schedule mismatched with the rest of the world.

"When I wake up in the morning, it’s like I'm fighting horse tranquilizers," says Park, a 34-year-old health care administrator who lives in Overland Park, Kansas. If she had it her way, she'd fall asleep around 3 am and wake up around noon.

You’re also subject to judgment if you’re groggy when others are at their peak, Park and others said.

"People didn’t believe me," she says of past interactions with employers and family. "They thought I was out partying all night, that I had a drinking problem or a drug problem or was just lazy. And it was none of those things."

For Amy, a 26-year-old Seattle resident, being a delayed sleeper means "there's a lot of emotional baggage tied up into going to work," she says. "You're arriving later, you feel like you're not actually present, when people ask you questions you give stupid answers." Then weekends become a time for catching up on sleep, not leisure. It’s a "terrible cycle," she says.

Being a morning (or evening) person is inborn, genetic, and very hard to change

"Our clocks don’t run on exactly a 24-hour cycle," Gehrman says. They're closer to 24.3 hours. So every day our body clocks need to wind backward by just a little bit to stay on schedule.

For the most part, the sun takes care of this. Exposure to bright light stimulates the brain's master clock — the suprachiasmatic nucleus — to wind back those three-tenths of an hour.

With night owls, a few things get in the way of this resetting process.

1) Genes: The suprachismatic nucleus is the body's master clock, but it isn't the only one. Every single cell of the body has clock genes, bits of DNA that flip on and off throughout the day. (Like the body as a whole, the cell's metabolism is scheduled for efficiency. Clock genes regulate the expression of between 5 and 20 percent of all the other genes in the cell.)

The expression of these genes is believed to feed back into the body's master clock and help set its time. Scientists have found that small variations in these genes lead to earlier or later rhythms in animals, and are beginning to identify the genes that cause the same effects in humans.

(Because it's genetic, chronotype is inheritable: Twin and heredity studies have found that about half the difference in chronotypes can be explained by genetics.)

2) How these genes push people earlier or later isn't precisely known. One thought is that evening-type people may have a body clock that runs longer than average. Evening types' clocks can run as long as 24.5 or 24.7 hours, Gehrman says. A longer clock means the suprachismatic nucleus has to work harder to make an adjustment. When it fails to readjust, sleep times drift later and later into the evening.

3) Later types may be more sensitive to light exposure at night. Bright light at any time of the day tells our bodies it's time to be awake. This wasn't a problem back in olden times, when the setting of the sun ended light exposure for the day. In modern times, light from our computers and televisions pushes some evening-type people to stay awake longer.

Once these chronotypes are set, they're frustratingly stubborn. "Our feeling at this point is that these are probably unchangeable characteristics," Lack says. (The only exception is when we age. As the decades pass, our clocks tend to shift earlier.)

When our personal clock is out of sync with society's, our health suffers

Scientists have a term for being out of sync: social jet lag. It’s a social nuisance for the people who have it, but it also puts stress on the body that may undermine health.

In a tightly controlled lab study, 24 healthy participants who had their sleep shifted by one hour each day (simulating jet lag) started to look prediabetic after a three week trial. Their resting metabolic rates dropped 8 percent. "Assuming no changes in activity or food intake," that "would translate into ~12.5 pounds increase in weight over a single year," the study, published in Science Translational Medicine in 2012, concluded.

When people experience social jet lag, they'll often try to make up for the sleep debt on the weekends. But this too is jarring for the body and makes waking up on Monday all the more difficult.

In 2012, researchers in Europe analyzed a self-report data set of 65,000 Europeans and found "social jet lag significantly increased the probability of belonging to the group of overweight participants." There's also correlational research indicating that late chronotypes may be at a greater risk for depression, and that they're more likely to engage in risky behaviors like smoking.

The hypothesis here isn’t that chronotype inherently causes these negative outcomes, but rather that a mismatched chronotype and daily schedule do.

A 2015 study tracking the sleep of 447 middle-aged adults for a week also picked up on this worrisome pattern. It found social jet lag correlated with insulin resistance — a precursor to diabetes — lower HDL cholesterol (the good kind), higher levels of triglycerides, higher waist circumference, and higher BMI. These correlations remained even after adjusting for behaviors like exercise, smoking, and alcohol use.

"What I think we’re showing here is that there’s some sort of importance about us ideally being able to work, wake, and match up our schedule as best as we can to what we are biologically suited for," Patricia Wong, the lab researcher on the 2015 paper, told me in December. She also stressed that these were exploratory correlational studies. More rigorous testing is needed to confirm the link.

If late sleepers want to wake up early, they're often hit with a double whammy. They'll be out of sync with society — which stresses the body — but they'll also be underslept. The research is a bit clearer on this: Short sleep appears to be a significant risk factor for heart disease, diabetes, and obesity.

In the academic literature, short sleep has been associated with higher blood pressure, body mass index, and increased calcification of the coronary artery. In lab experiments, people who slept only five hours a night for one week became less sensitive to insulin, which makes it harder to maintain blood sugar levels. In an overnight sleep study of 1,024 individuals, poor sleep was associated with the misregulation of the hunger hormones leptin and ghrelin, which would explain another finding: that when people are denied sleep, they have increased appetite.

"I don’t want people to panic and think they’re going to die if they don’t follow their body's rhythm," Gehrman says. "It’s a general health issue: Following your body is ideal."

Delayed sleep phase is very, very hard to treat

Generally there are two treatment options to shift evening people’s clocks earlier in the day. But they require constant vigilance and are hard to maintain.

The first — and easiest — is a combination of bright light therapy and melatonin. Exposure to bright light in the morning helps reset the body's clock to an earlier time. Patients can buy specialty lamps for this, or just make an effort to go outside early. (Anyone who wants to try to be more of a morning person can try this.)

Those who try light therapy also have to be mindful of sticking to an earlier sleeping schedule. "Sleeping late on weekends can ruin whatever progress is made," Charmane Eastman, who studies biological rhythms at Rush University, writes me in an email. "It's like slipping off of a food diet."

Melatonin also pushes back the clock, but only if the dose is timed correctly — it's most effective when it’s taken several hours before bed. (Even though melatonin is available over the counter, the clinicians I spoke with recommended seeing a sleep specialist to get the timing right.)

The second treatment is chronotherapy. Here, instead of pushing the body's clock backward it's wound forward. For a few weeks, a patient will go to bed two hours later every night until she reaches her desired sleep time. "It can work very well, but very few people have the absolute, total control of their schedule for the two weeks that it takes to do that," Gehrman says. Very few of his patients choose this option.

Park, the 34-year-old health care administrator, tried chronotherapy and gave up. It was too hard to maintain.

"As soon as one little thing gets knocked off, you just revert right back," she says. It can takes weeks for her to get on a "normal" sleep schedule, and in one night (perhaps there's an poorly timed flight, or a birthday party) of sleeping later to go right back to the start. "When I travel [for work] and come back home, I’m all fucked up again, without fail."

According to Raj Dasgupta, a fellow at the American Academy of Sleep Medicine, the relapse rate for delayed sleep phase patients is around 90 percent. "There are individuals who are trying to accommodate to society, to work, and despite their efforts and many, many treatments, they can’t do it," Dasgupta says.

Toward a "chronotype acceptance" movement

Simply put: Society favors early risers. Think no further than phrases like, "The early bird catches the worm."

Getting an official diagnosis can help lift the burden from people on a different clock. "It really helps to know it isn't my fault," Sokolis says of her diagnosis. But people like her are still left with a hard choice. The best-paying jobs start in the morning. Educational opportunities do, too. Can they really afford to miss out on everything that happens before noon?

The delayed sleep phase sufferers I spoke to all agreed: The one thing they wished for was greater tolerance of people like them.

"Sometimes one of the helpful things I do for people is give them permission to follow a late schedule," Gehrman says of his clinical practice. "Because there’s an attitude in our culture that there is something wrong with that."