Morning lark or night owl? Chronotypes explained

Your body has a clock

Almost every cell in your body runs on a roughly 24-hour rhythm, coordinated by a small area in the brain that responds to light. This circadian clock controls when you feel sleepy, when your body temperature peaks and when you are most alert. Your chronotype is where your personal clock sits compared with other people's: earlier, later or somewhere in between.

Most people are intermediate types. Smaller groups are clearly early (larks) or clearly late (owls).

What shapes your chronotype

• Genes. Twin studies and large genetic studies show that chronotype is partly inherited. Several genes involved in the body clock have been linked to being a morning or evening person.
• Age. Children tend to be early. During adolescence the clock shifts later, peaking around the end of the teenage years, then gradually moves earlier again throughout adulthood.
• Light. Morning daylight pulls the clock earlier; bright screens and lights late at night push it later.

That is why a sixteen-year-old who can't fall asleep before midnight isn't just being difficult. Their clock genuinely runs later than their parents'.

Social jet lag

Chronobiologist Till Roenneberg coined the term social jet lag for the gap between when your body wants to sleep and when work or school forces you to wake. Night owls on a 9-to-5 schedule live in a mild, permanent jet lag during the week, then sleep in on weekends, which shifts their clock even later. Studies link large amounts of social jet lag to poorer sleep, lower mood and daytime fatigue.

Tips for night owls

• Get bright light early. Go outside within an hour of waking, even on cloudy days.
• Dim the evening. Lower lights and screen brightness for the last hour or two before bed.
• Keep weekends close to weekdays. Sleeping in for three extra hours on Saturday makes Monday harder.
• Protect your peak. Do demanding work later in the day if you can, and save routine tasks for the morning.

Tips for early birds

• Use your mornings. Put the hardest thinking in the first few hours.
• Plan for evening events. A short afternoon rest can help you enjoy a late dinner without fading.
• Be kind to the owls around you. Early-morning messages and meetings can feel like an ambush to them.

When couples are out of sync

A lark and an owl in the same home is a classic quiet source of friction: one partner wants to chat at breakfast, the other can barely speak; one wants to talk late at night, the other is half asleep. Some practical approaches:

1. Find your overlap. Identify the hours when you are both reasonably alert and use them for important conversations and shared time.
2. Agree on bedtime rituals. Going to bed together and the owl getting up again later can preserve closeness without forcing the same sleep schedule.
3. Don't moralise. Neither rhythm is more virtuous. Early rising has a better reputation, not better character.

The TraitMix chronotype test estimates your peak focus window and, in group comparisons, draws everyone's windows on a 24-hour strip so you can see the shared hours at a glance.

This guide is general information. If you have persistent trouble sleeping, loud snoring or extreme daytime sleepiness, please see a doctor.

Frequently asked questions