Are you one of those people who rises before dawn and never needs an alarm clock? Or would you happily sleep until midmorning if you could? Do you feel like you are just hitting your stride by late afternoon, or do you get the day’s main tasks accomplished by lunch?
Most of us have some degree of preference for late nights or early mornings. Where an individual falls on this spectrum largely determines his or her chronotype—an individual disposition toward the timing of daily periods of activity and rest. Some of us are clearly “larks”—early risers—while others are distinctly night owls. The rest of us fall somewhere between the two.
We’re now learning that these night owl and early riser tendencies are driven to some significant degree by biological and genetic forces. Different chronotypes are associated with genetic variations, as well as differences in lifestyle and mood disposition, cognitive function, and risks for health problems including sleep disorders and depression.