(The following excerpt from Night Owls and Early Risers Have Different Brain Structure by Michael J. Breus, Ph.D., was published on November 14, 2013, on psychology today.com. To view it in its entirety click on the link below.)
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 day’s stride by late afternoon, or do you like to get the big tasks of the day accomplished early? 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 of us are distinctly night owls. The rest of us fall somewhere in between the two.
We’re learning that these night owl and early riser tendencies are driven by 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.
New research has now found evidence of physical differences in the brains of different chronotypes. Scientists at Germany’s Aachen University conducted brain scans of early risers, night owls, and “intermediate” chronotypes who fell in between the two ends of the spectrum. They discovered structural differences in the brains of people with different sleep-wake tendencies. Researchers observed a group of 59 men and women of different chronotypes: 16 were early risers, 20 were intermediate sleepers, and 23 were night owls. They found that compared to early risers and intermediates, night owls showed reduced integrity of white matter in several areas of the brain. White matter is fatty tissue in the brain that facilitates communication among nerve cells. Diminished integrity of the brain’s white matter has been linked to depression and to disruptions of normal cognitive function.