Sunlight may be the key to treating attention deficit hyperactivity disorder (ADHD), according to a new study. Researchers at Brainclinics in the Netherlands have discovered an interesting correlation between sunny climates and lower rates of ADHD among children and adolescents. The findings may inspire new integrative treatments for the psychiatric disorder that currently affects between five and seven percent of the global population.

The study examined data maps released by the U.S. Centers for Disease Control and Prevention (CDC) in an effort to highlight possible environmental factors of ADHD. Intriguingly, the prevalence rates of the disorder appeared to be reduced in geographical areas that enjoyed more sunlight. The apparent link persisted when the researchers controlled for other factors known to influence the disorder.

The team theorizes that sunlight may benefit individuals with ADHD by fortifying our circadian rhythm — the biological clock that helps us distribute energy throughout the day. In the past, sleep disorder treatments developed to restore this rhythm have proven effective. Similarly, light exposure therapy is sometimes used to alleviate symptoms.

Although the study falls short of establishing a causal relationship between increased sunlight and a reduction in ADHD prevalence, the researchers are confident that the findings will be of use for public health and education officials. For example, new technologies could be designed to emulate the effects of sunlight. “From the public health perspective, manufacturers of tablets, smartphones and PCs could investigate the possibility of time-modulated color-adjustment of screens, to prevent unwanted exposure to blue light in the evening,” lead researcher Martijn Arns said in a press release.

Similarly, the possible “protective” effect of sunlight could be incorporated into classrooms and lecture halls. “These results could also point the way to prevention of a sub-group of ADHD, by increasing the exposure to natural light during the day in countries and states with low solar intensity,” Arns explained “For example, skylight systems in classrooms and scheduling playtime in line with the biological clock could be explored further."

Still, the correlation between ADHD and sunlight is in need of further research. According to John Krystal, chairman of the Department of Psychology at Yale University and editor of Biological Psychiatry, the link is as exciting as it is problematic.

"The reported association is intriguing, but it raises many questions that have no answers," he told reporters. "Do sunny climates reduce the severity or prevalence of ADHD and if so, how? Do people prone to develop ADHD tend to move away from sunny climates and if so, why?"

Source: Arns M, Van Der Heijden KB, Arnold LE, Kenemans L. Geographic Variation in the Prevalence of Attention-Deficit/Hyperactivity Disorder: The Sunny Perspective. Biological Psychiatry. 2013.