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Night owl, not early bird: chronotype, sleep and the best time for hard tasks

2026-09-28 · 4 min read

Later – biologically

A review of 62 studies consistently found a later chronotype in ADHD and signs of a delayed internal clock, such as later evening melatonin release (Coogan & McGowan 2017). Reviews report very high rates of sleep-onset problems, but the exact figures vary between studies.

The synchrony effect

People who work in their own peak tend to do better on demanding, analytical tasks. This is most robust for clear morning or evening types (May, Hasher & Healey 2023, general population). It hasn't been studied specifically in ADHD.

Gauge your chronotype roughly

• Look at free days without an alarm: when do you fall asleep, when do you wake up?
• The middle is your mid-sleep. If it's well after 4 am, you're more of an evening type.
• If you slept too little during the week, you'll sleep longer at the weekend – that shifts the midpoint. Subtract a little in your head.

That's the core idea of the Munich Chronotype Questionnaire. It's an estimate, not a diagnosis.

Short nights: plan less, not more

After several nights of 6 hours of sleep, performance in a lab study kept falling day after day – but felt sleepiness hardly rose (Van Dongen et al. 2003, general population). So the effect is easy to underestimate. Sleep societies recommend 7 hours or more for adults on a regular basis.

Persistent problems falling or staying asleep are something to discuss with a doctor.

How Klarnext handles it

With an Apple Watch, Klarnext estimates your internal clock from mid-sleep on free days and places hard tasks in your personal peak. After a short night (under 6 hours), or when the last three nights were clearly shorter than usual, Klarnext plans at most two must-dos and more room. Klarnext deliberately ignores sleep stages – watches are too imprecise for that.

This article provides general information and does not replace medical, psychological or therapeutic advice.