Sunny Regions Reflect Lower ADHD Rates: Study10/29/13
TUESDAY, Oct. 29 (HealthDay News) -- Sunny days can be a big
distraction for those who are tethered to their desks, but a new
study suggests that sunlight may actually lower the prevalence of
attention-deficit/hyperactivity disorder (ADHD).
Scientists mapped the number of ADHD diagnoses across the United
States and in nine other countries. They compared those rates to
the intensity of sunlight those regions receive year-round.
Regions that got the most sun had rates of ADHD diagnoses that
were about half as high as regions that got the least, according to
"The maps line up almost perfectly," said study author Martijn Arns, director of Brainclinics, in the department of experimental psychology at Utrecht University in Nijmegen, Netherlands.
In the United States, the sunniest states were in the Southwest
and West and included Arizona, California, Colorado, Nevada, New
Mexico and Utah. Rates of ADHD diagnoses in those states ranged
from 6 percent to 8 percent. In the darkest states, which included
a swath of the Northeast, rates of ADHD ranged from 10 percent to
The relationship between ADHD and sunlight held steady even
after researchers adjusted their data to control for other factors
that might account for differing rates of ADHD diagnoses, such as
race, poverty and the male-to-female ratio in each area.
Researchers even considered whether vitamin D, which is produced
in the body after exposure to sunlight, might account for the
differences, but they said a prior study ruled that out.
They also examined whether more sunlight might be tied to lower
rates of other kinds of mental disorders, including depression and
autism. It wasn't.
The researchers admitted that the link could just be a
coincidence, and there isn't necessarily a cause-and-effect
relationship between sunny climates and lower rates of ADHD
diagnosis. But since some children and adults with ADHD have
disrupted body clocks, which are regulated by light, they believe
the relationship deserves further investigation.
Arns said about 80 percent of adults and about one-third of
children with ADHD have trouble falling asleep at night. Some
studies have found that these night-owl tendencies are driven by a
delayed peak in the sleep hormone melatonin.
Melatonin seems to be especially disrupted by the blue
wavelengths of visible light, Arns said. Energy-saving LED light
bulbs, as well as the screens of tablets, smartphones and computers
emit blue light. When people use those devices in the evening, it
can delay melatonin release and disrupt sleep.
But Arns said people who live in sunny climates may get some
natural protection from this sleep upset because they get a healthy
dose of bright light in the morning, which keeps their body clocks
He's currently exploring ways to test his theory.
An expert who was not involved in the study, which was published
in the Oct. 15 issue of the journal
Biological Psychiatry, said he's not sure melatonin is the
Children in sunny climates may spend more time playing outside,
for example, said Dr. Andrew Adesman, chief of developmental and
behavioral pediatrics at the Steven & Alexandra Cohen
Children's Medical Center in New Hyde Park, N.Y.
"There's a small but growing literature talking about exercise as a way to moderate ADHD and hyperactivity," Adesman said. "There could be other variables that are responsible."
Centers for Disease Control and Preventionfor more on ADHD.
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