Researchers from the Department of Psychiatry at the University of Utah analyzed data from the 2007 National Survey of Children's Health report and 2010 National Survey of Children with Special Health Care Needs report to identify and compare the prevalence of ADHD diagnoses among youth aged 4 to 17 living in the 48 adjoining states and the District Columbia.
The researchers found that states with higher than average elevations were most likely to have lower ADHD diagnosis rates, with every one foot increase in average elevation above sea level decreasing diagnosis rates by 0.001 percent. Nevada, which has an average elevation of 5,517 feet above sea level, had the lowest percentage of ADHD diagnoses at 5.6 percent, followed by Utah at 6.7 percent. ADHD diagnoses were more prevalent in states with average elevations less than 1,000 feet above sea level, with North Carolina—869 feet above sea level—having the highest diagnoses rates at 15.6 percent.
The researchers speculate that the decreased rate of ADHD may be due to higher levels of dopamine produced as a reaction to hypobaric hypoxia—a condition caused by breathing air with less oxygen at higher elevations. Decreased dopamine levels have been associated with ADHD so when levels of the neurotransmitter increase with elevation, the risk for getting the disorder diminishes, the study noted.
Coauthor Perry Renshaw, M.D., Ph.D., M.B.A., a professor of psychiatry at the University of Utah, emphasized that the current findings are not implying that people should start moving to the mountains to decrease the risk for ADHD in children. However, the research results do have potential implications for treating the disorder, which may involve increasing dopaminergic activity.
To read more about other environmental factors that have been suggested to affect rates for ADHD, see the Psychiatric News article "Sunbaked Regions Often Show Lower ADHD Prevalence."