Geographic variation in the prevalence of ADHD (Circadian and sleep aspects)

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A study published today in Biological Psychiatry sheds new light on the increasing rates (prevalence) of attention-deficit/hyperactivity disorder, known as ADHD. Children with ADHD have problems with inattention, distractibility, disorganization, impulsiveness, and overactivity. This study found that “sunny” regions with high solar intensity, such as the US states of California, Arizona, and Colorado, and countries like Spain and Mexico have lower prevalence of ADHD. An apparent protective effect of sunlight accounted for 34-57% of the variance in ADHD prevalence. The authors speculate that this may be related to sunlight’s effects on preventing circadian rhythm (“biological clock”) disturbances. These results suggest ways to prevent or treat ADHD for a substantial sub-group of patients.