Chronotypes Explained: Are You a Lark, an Owl, or Somewhere in Between?

Most people are neither larks nor owls. Chronotypes run from strongly morning to strongly evening, and the bulk of adults sit between the two ends. In a nationally representative US study of time-use diaries, chronotype formed a near-normal bell curve, with most people near the middle and strong larks and owls at the thin tails, Dorothee Fischer and colleagues reported in 2017.¹

Where you sit on that curve depends on your genes, your age and the light you get, and it drifts over a lifetime. That makes your chronotype worth knowing and a poor label to build an identity on. Finding yours needs no quiz, only your own sleep times on days without an alarm.

For the everyday habits behind better nights, start from the guides to sleep and rest.

How chronotypes are measured, and how to place yourself

Researchers measure chronotypes in two validated ways: by asking which hours you would choose, with the Morningness-Eveningness Questionnaire (MEQ) that Jim Horne and Olov Östberg published in 1976, or by recording when you actually sleep on free days, with the Munich ChronoType Questionnaire (MCTQ) that Till Roenneberg’s group introduced in 2003.³⁴

The MEQ asks what time you would pick for your activities if the choice were entirely yours.² In Horne and Östberg’s small validation study, which sorted people into morning, evening and intermediate types, the morning types reached their daily peak in body temperature earlier than the evening types, a sign the questionnaire tracks the body clock and not only taste.³

The MCTQ asks what you actually do. It takes the halfway point of your sleep on days off, when no alarm decides for you, and corrects it for people who sleep longer on those days to pay back the sleep debt a short working week builds. Its developers report that it has been validated against more objective measures of daily timing in several independent studies.²

Workdays hide chronotype, which is why both tools look past them. A colleague who is up early all week can seem a natural early riser until a free Saturday, when she sleeps until mid-morning: the alarm was doing the work. Demanding tasks can then be planned around the result, as the guide to finding your peak hours for focused work sets out.

Larks and owls are the two ends of one bell curve

In the Fischer study, chronotype estimated from the midpoint of weekend sleep followed a near-normal distribution overall and within each age group, which means the familiar labels are bands cut from one continuous scale rather than two camps.¹

The study

Moderate evidence

One bell curve from a US diary survey (2017)

Chronotype, estimated from when people slept at weekends, followed a near-normal distribution in the whole sample and within each age group. Very early and very late types were rare and sat at the tails.¹

Height works the same way: “tall” is a useful word, but nobody is born into a tall group or a short group. The data come from one country and from self-reported diaries, so the exact shape may differ elsewhere.

In practice, “somewhat later than most” is a more useful description than “owl”: it says your preferred hours differ from the office’s by a little, and ordinary habits may bridge the gap.

Myth

Everyone is either a morning person or a night person.

Fact

Chronotype is a continuum. In a large US diary study most people sat near the middle, and strong larks and owls were a minority.

Genes tilt you earlier or later, by minutes rather than hours

Chronotype is partly inherited through many gene variants, each with a tiny effect. A team led by Samuel Jones, writing in Nature Communications in 2019, drew on nearly 700,000 people in the UK Biobank and customers of the consumer genetics company 23andMe and linked 351 regions of the genome to being a morning person, including genes already known to run the body clock.⁵

Size is the surprise. The 5 percent of people carrying the most morning-linked variants had sleep timing about 25 minutes earlier, measured with wrist activity monitors, than the 5 percent carrying the fewest.⁵ Two caveats sit alongside it: the participants were of European ancestry, and two authors were employees of 23andMe, whose customer data the study used.⁵

Because each variant adds so little, inheritance sets a leaning, not a timetable. A family where both parents are up at dawn and the teenager sleeps until noon shows genes and age pulling in different directions. Two weeks of your own free-day sleep times are worth more than any gene report.

Light and age move your body clock, whatever your genes

Light and darkness are the main signals that set the body clock.² In a 2013 study in Colorado, US, Kenneth Wright’s team took 8 adults camping for a week with only natural light; their melatonin rhythm moved about two hours earlier and began near sunset, and later types shifted the most.⁶

The mechanism is timing. Light in the morning tends to move the clock earlier and light in the evening tends to move it later, as the 2015 US sleep medicine guideline summarizes the research.⁷ Roenneberg’s team argue that living indoors by day under electric light at night has pushed body clocks later and widened the gap between early and late types.² Eight campers is a very small sample, so read the size of the shift as an illustration, not a forecast for you.

Consider an office worker who commutes in winter darkness, sits under indoor lighting all day and reads on a phone until midnight. Part of what feels like a fixed owl nature may be that light pattern, and more daylight early in the day with dimmer evenings is the part within reach, where work and caregiving allow.

Age moves the clock too. The Fischer diaries show chronotype drifting later across adolescence, reaching its latest point at about 19 and moving earlier from then on.¹ Roenneberg and colleagues, reviewing their questionnaire data in 2019, describe the same arc and name genes, light and age as the three main sources of the spread.²

Night owl health headlines: what the risk figures leave out

Evening types have higher rates of several health problems in observational studies, but the headline figures are relative risks, small or unreported in absolute terms, and partly explained by owls living on morning schedules.

The best-known example comes from the UK Biobank. Kristen Knutson and Malcolm von Schantz followed more than 400,000 middle-aged and older UK adults for about six and a half years and found that definite evening types had a slightly higher risk of death than definite morning types, about 10 percent higher after adjustment.⁸ That is a relative figurerelative and absolute risk: Two ways to state the same difference. Relative risk compares the chance of an outcome in one group with another, as a ratio; absolute risk says how many extra or fewer people per hundred it affects. A large relative change can be a small absolute one when the outcome is rare.Full entry in the glossary, and the paper does not report death rates for each chronotype group. Across the whole cohort, roughly 2 in 100 people died during follow-up, so as an illustrative sum, 10 percent more on that base would be a fraction of one extra death per 100 people.

Mood is where the evidence is more careful. A 2021 genetic study by Iyas Daghlas and colleagues used gene variants linked to earlier sleep timing as a natural experiment, a method designed to reduce confounding, and found that a sleep midpoint one hour earlier was linked to about 23 percent lower odds of major depressiondepression: A common mental health condition in which low mood or loss of interest lasts most of the day, nearly every day, for weeks, along with changes such as poor sleep, tiredness or trouble concentrating. It is diagnosed by a clinician, and effective treatments exist.Full entry in the glossary.⁹ The absolute size is not reported, and the method rests on assumptions that cannot all be tested.

Social jet lag muddies the picture further. Owls on early schedules often sleep less and at the wrong time for their clock, and observational studies struggle to separate the clock from the timetable.²

The practical lesson is a three-question check whenever you read that night owls die sooner or are more often depressed: compared with whom, how many people in absolute terms, and could the schedule rather than the clock explain it? If you are a strong owl whose mood has been low for weeks, that alone justifies a talk with a doctor.

Lions, bears and wolves: why animal quizzes are not a measure

The popular four-animal scheme of lion, bear, wolf and dolphin comes from a 2016 popular book, The Power of When, by the US psychologist Michael Breus. None of the sources reviewed here validates it against research measures such as the MEQ.

Breus’s own quiz site describes chronotypes as a spectrum and then sorts that spectrum into four animal categories. The research above describes a continuum, so any four-way split puts near neighbors into different animals and very different people into the same one.¹

Consumer “chronotype” gene tests share a weakness: if even the people with the most and the fewest morning-linked variants sleep only about 25 minutes apart, a report built on a handful of variants says little about one person.⁵

If you enjoy the quiz, treat the result as a conversation starter. For anything you plan your week around, use your free-day midpoint or a validated questionnaire such as the MEQ.

When a late body clock becomes a sleep disorder

A late chronotype becomes delayed sleep-wake phase disorder only when the late timing is long-lasting, cannot be moved to the hours your life requires, and causes trouble falling asleep at a conventional bedtime or sleepiness and problems by day, as the American Academy of Sleep Medicine’s 2015 US guideline describes it.⁷

The telling sign is what happens when you are free to choose. People with the disorder usually sleep normally in length and quality on a late schedule, on holidays for instance; the problem is timing, not an inability to sleep.⁷ Picture a student who for months cannot fall asleep until the small hours, misses morning lectures and is exhausted on weekdays, yet sleeps soundly into late morning during the break.

The US guideline describes timed melatonin as a treatment for adults with the disorder, with a conditional (weak) recommendation based on limited evidence, and treatment is planned with a clinician because the timing matters.⁷ Melatonin’s legal status varies: in the US it counts as a dietary supplement, while several other countries treat it as a prescription drug. Before anyone takes it, the US National Center for Complementary and Integrative Health tells people to check with a health professional in pregnancy or while nursing, alongside other medicines, or before giving it to a child.¹⁰ Readers elsewhere can ask a pharmacist what applies locally.

From urgent to routine: when a late clock needs a doctor

Drowsy driving and thoughts of self-harm call for action right away, a late schedule that will not shift despite months of trying deserves a doctor within weeks, and the rest can wait for a check-up. The tiers are this article’s grouping; the named bodies wrote the advice.

• Now. Do not drive while fighting sleep. If drowsiness hits on the road, the US National Institute for Occupational Safety and Health says to get off the road at the first exit or rest stop and stop driving.¹¹ If sleep problems arrive alongside thoughts of suicide or self-harm, call your local emergency number or a crisis line. In the US, the National Institute of Mental Health lists the 988 Suicide and Crisis Lifeline.¹² The NHS in the UK gives Samaritans (116 123) as a listening line and 999 when a life is at risk.¹³ In other countries, local emergency services can connect you to a crisis service.
• Soon. Book a doctor’s visit if you have been unable to fall asleep or wake at the times you need for months, despite steady habits, or if daytime sleepiness is affecting work or driving. For sleep problems lasting months, or ones that leave you struggling to cope day to day, the UK’s NHS says it is time to see a GP.¹⁴ A doctor can check for delayed sleep-wake phase disorder and refer you to a sleep specialist.
• Routine. Bring up low mood that lingers, or a late schedule that keeps clashing with work, at your next appointment. A written record of a week or two of sleep times gives the doctor something concrete to go on.

The bottom line

Treat your chronotype as a place on a curve that moves, not an animal you were born as. Place yourself using free-day sleep times or a validated questionnaire, expect it to shift with age and light, and read night owl health headlines for the absolute numbers and the schedule behind them. When a late clock stops you from living the hours you need, month after month, that is a matter for a doctor rather than a quiz.