Chronotype: What Research Shows

What chronotype means

Chronotype is a person's usual preference for the times of day when they sleep and are active. In research it is most often measured with questionnaires. [1] Being a "morning person" is described by researchers as a behavioral sign of a person's underlying body clock (circadian rhythm). [2] Questionnaire scores sit along a range, and researchers pick cutoff scores to label morning and evening types. [1] This page is information only and does not tell you which type you are or how to change it.

How chronotype is measured

• Questionnaires. The two most used are the Morningness-Eveningness Questionnaire (MEQ) and the Munich Chronotype Questionnaire (MCTQ). [1]
• MCTQ. It asks about real sleep times on work days and free days. A Czech study of 2,703 adults found its main chronotype score, mid-sleep on free days corrected for weekday sleep debt, was significantly related to MEQ scores, and the authors judged the two questionnaires substitutable. [1] The MCTQ's creators note it has been translated into 13 languages and checked against more objective measures of daily timing in several independent studies. [3]
• Not interchangeable everywhere. In 55 teenagers who also wore activity monitors for a week, three chronotype questionnaires were valid, but two of them sorted people into morning and evening types differently and the authors said they cannot be used interchangeably. [4]
• Direct, estimated, scored. Questionnaires record what people report (direct but subjective). A mid-sleep time is calculated from those answers (derived). An app or wearable "chronotype" label is a proprietary score, and Proper evidence not found for consumer wearable or app chronotype labels: we searched PubMed for validation studies of wearable and app chronotype estimates and found none usable.

Genetics and daily timing

A genome-wide study of 697,828 people found 351 genetic regions linked with being a morning person. In 85,760 people with activity-monitor data, those carrying the most morningness variants had average sleep timing about 25 minutes earlier than those carrying the fewest. [2] That is a modest difference, so genes alone do not set a person's sleep timing.

Eveningness, mood and health

• Mood. A meta-analysis of 36 studies (15,734 people) found a small link between eveningness and more depressive symptoms (effect size -0.20). The authors said longer-term studies are needed to tell which comes first. [5] Label: mixed to promising but limited, because the link is a correlation.
• Mental health, genetic approach. The genome-wide study's authors report that being a morning person is causally associated with better mental health but not with body mass index or type 2 diabetes risk. [2] This is one analysis and needs replication.
• Illness and death. In the UK Biobank (433,268 adults, average 6.5 years of follow-up), definite evening types had a higher risk of death from any cause than definite morning types (hazard ratio 1.10, 95% CI 1.02 to 1.18) after adjusting for several factors. Chronotype was based on a single self-reported question. [6] The authors suggest this may reflect behavior and a mismatch between body timing and work or social schedules, not eveningness itself. [6] Label: mixed; observational findings cannot prove cause.

A mismatch, not a flaw

The researchers who built the MCTQ describe "social jetlag" as one idea arising from their work. [3] In plain terms, the concern is a gap between a person's body timing and the schedule imposed by work or school. [6] That is why a night owl with a flexible schedule may face different issues than one with early shifts. See shift work and circadian disruption.

How to judge chronotype claims

• Ask whether the claim comes from a validated questionnaire or a brand's own score.
• Treat "your chronotype is X, so do Y" plans as marketing claims unless a trial tested them.
• Remember that small average differences do not predict one person's health.

Related reading: Sleep timing and regularity, Circadian biology explained and morning light and the circadian rhythm.