Sunlight, ADHD, Blue Light, ADD

New research is beginning to shed light on the relationship between sunlight, sleep, and screen time (like computers and television sets) and attention deficit hyperactivity disorder (ADHD) and how the latter might be affected by the former, says ADHD expert Dr. L. Eugene Arnold.

ADHD is a neurodevelopmental disorder often characterized by abnormal degrees of inattention, impulsivity, as well as hyperactivity, or some combination thereof. ADHD is the most frequently diagnosed and observed neurodevelopmental disorder in children, but it often carries on into adulthood.

According to Dr. Arnold, who is a professor emeritus of psychiatry at the Ohio State University, an estimated 13 million men, women and children in the USA alone meet the diagnostic requirements of ADHD.

Solar Intensity and ADHD

Dr. Arnold also worked along side Dr. Martijn Arns of the Netherlands and together they published an insightful paper in Biological Psychiatry that sheds light (no pun intended) on the increasing rates of ADHD that we have been observing around the world. The study found that regions with more sun and with higher solar intensity (such as the US states of California and Arizona, or countries like Mexico or Spain) have a substantially lower presence of ADHD. What is reported as a protective effect of sunlight accounted for between 35-55% of the variation in the prevalence of the condition, indicating a strong involvement. The scientists behind the study suggest that the relationship may revolve around the ability of sunlight to protect against disturbances to a person’s circadian rhythm, otherwise known as their biological clock.

To come to this suggestion, the researchers from Utrecht University, Leiden University, and Ohio State University analyzed ADHD rates by state and compared them to solar intensity maps and observed a striking overlap. Solar intensity is a measure of the amount of sunlight an area receives.

States with a lower solar intensity saw ADHD rates as high as 10-12%, which stark contrast to states with higher degrees of solar intensity.

Those states have about, say, 5 or 6 percent rate of ADHD. So, it’s about a 2-to-1 ratio, says Arnold. There are many possible explanations. For example, with more sunlight, maybe kids get out more to play and get more of the exercise that, increasingly, we know is good for brain function.

This is not to suggest, however, that sunlight is the only contributing factor. Dr. Arnold also highlights recent studies, which implicate sleep as a potential cause, since people with ADHD exhibit similar traits to those who are deprived of sleep.


There’s a correlation with things like irritability, impulsiveness, inattentiveness – which are core symptoms of ADHD, says Arnold. And what’s robbing them of sleep may be their computer and TV screens. They emit a blue light that could be disrupting melatonin, which is the hormone that helps regulate sleep. Children’s duration of sleep has decreased over the past decade or two, since the introduction of those electronic devices.

Blue-Light a Culprit

The studies authors suggest that the delayed circadian rhythm and subsequent difficult in sleeping may be a result of increased evening use of personal computers, tablets, smartphones, and other devices that emit light in the blue spectrum during evening hours.

By preventing the onset of melatonin, blue light delays the onset of sleep and that disrupts the sleep-wake cycle,” says Arnold. “More studies are needed to better understand these potential connections with ADHD.

Interestingly, these experts suggest that the rates of ADHD may be lower in states with higher degrees of solar intensity because the sunlight may override the blue-light emitted from TVs and other screens.

The main value of this particular study is that it opens up new vistas, new things to be investigated that maybe we hadn’t quite thought about before, says Arnold.


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