What is a chronotype, and can it change?

Short answer: Your chronotype is the time of day your body clock naturally prefers for sleep and activity, on a scale from very early to very late. Most people fall somewhere in between. Genes set part of it, but it also shifts with age and with how much daylight you get.

Is chronotype the same as circadian rhythm?

Not quite, though the two are closely linked. Your circadian rhythm is the roughly 24-hour cycle in sleep, hormone release, digestion and body temperature that nearly everyone has. Your chronotype describes when that cycle runs compared with the clock on the wall.

Different people synchronise to the same day and night earlier or later. These are the familiar larks and owls, and most people sit between the two extremes.

How many chronotypes are there, and is it scientific?

There is no fixed number. Chronotype varies smoothly from very early to very late, and research questionnaires place you on that scale. Named groups such as morning, intermediate and evening types are cut points on it, not separate kinds of people.

The idea itself is well grounded. The Morningness-Eveningness Questionnaire, published in 1976, sorted people into morning, evening and intermediate types, and morning types reached their daily peak in body temperature significantly earlier than evening types. Popular quizzes that sort people into four animals are a shorthand, not a research system.

Is chronotype genetic?

Partly. A 2019 study of genetic data from 697,828 people found 351 regions of the genome linked with being a morning person. Their combined effect on sleep timing is modest, though: the 5% of people carrying the most morning-linked variants slept about 25 minutes earlier, on average, than the 5% carrying the fewest.

The rest comes from your surroundings and your stage of life. Researchers name three main sources of difference between people: genes, light exposure and age.

Can your chronotype change?

Yes, within limits. Chronotype gets later from about age 10 until around age 20, then slowly moves earlier for the rest of life. That is one reason teenagers find early school starts so hard; see how circadian rhythm changes with age.

Light moves it too. In a small 2013 study, eight adults spent a summer week camping with only natural light. Afterwards, all measured markers of their internal clocks were about two hours earlier, and the later types shifted the most. The team behind the Munich ChronoType Questionnaire suggests that, in everyday life, chronotype may be more a state than a fixed trait.

So more morning daylight and dimmer evenings tend to pull a late rhythm earlier. Practical steps are in how to reset your circadian rhythm.

What chronotype am I?

A quick check uses free days, when no alarm wakes you. Over a week or two, note when you fall asleep and wake up, and find the midpoint. Mid-sleep on free days is the measure the Munich ChronoType Questionnaire uses, and the earlier it is, the earlier your type.

For example, sleeping from 1 a.m. to 9 a.m. gives a mid-sleep of 5 a.m. Long catch-up sleep after a short week makes you look later than you are, so the questionnaire corrects for it. In one example from its authors, an early type had a corrected mid-sleep of 1 a.m. and a late type 6 a.m. Other methods, from questionnaires to activity data, are covered in how to find your circadian rhythm.

How Actogram looks at this

Actogram is a MedTech company whose focus is the body clock. It reads the daily rhythm of rest and activity from ordinary minute-level step counts from a phone or watch, with no heart rate or sleep stages needed. It reads that rhythm from the daytime activity pattern, not only from night sleep. Today its tools are for research and wellness use and do not diagnose, treat or prevent any condition.

Sources

• Chronotype and Social Jetlag: A (Self-) Critical Review, Biology, 2019
• Social jetlag: misalignment of biological and social time, Chronobiology International, 2006
• Genome-wide association analyses of chronotype in 697,828 individuals provides insights into circadian rhythms, Nature Communications, 2019
• A self-assessment questionnaire to determine morningness-eveningness in human circadian rhythms, International Journal of Chronobiology, 1976
• Entrainment of the human circadian clock to the natural light-dark cycle, Current Biology, 2013
• Circadian Rhythms, National Institute of General Medical Sciences, 2023

General information, not medical advice. If sleep or tiredness problems affect your daily life, talk to a doctor. Reviewed 6 November 2026 by the Actogram team.