The numbers also show that 15.3 percent of pre-schoolers were taking dietary supplements, though there are no proven dietary treatments for the disorder, said Steven Cuffe, chairman of the Department of Psychiatry at the University of Florida College of Medicine in Jacksonville, and one of the authors of the study.
"We think there may be an issue with the availability of behavioral treatments for pre-schoolers," Cuffe said. "That is our suspicion. That [number receiving behavioral therapy] should be higher."
Ileana Arias, principal deputy director of the Centers for Disease Control and Prevention, which also took part in the study, said in a statement that "we do not know what the long-term effects of psychotropic medications are on the developing brains and bodies of little kids. What we do know is that behavioral therapy is safe and can have long-term positive impacts on how a child with ADHD functions at home, in school and with friends."
According to the National Institute of Mental Health, ADHD is one of the most common childhood brain disorders. Youngsters can have difficulty staying focused on a task, paying attention and controlling their behavior and can be hyperactive.
Three different types of drugs -- the stimulant Ritalin is probably the most well-known -- are prescribed for treatment. Some can have side-effects on children, including depressing their appetite and causing difficulty sleeping.
According to the research, which was published online Wednesday in The Journal of Pediatrics, there were 6.4 million children aged 4-17 -- 11 percent of that population -- with a diagnosis of ADHD in 2011. Seventy-four percent had received medication in the previous week, 44 percent had received behavioral therapy in the previous year, and 10.2 percent had taken dietary supplements in the previous year.
For school-aged children, Cuffe, said, medication alone or a combination of drugs and behavioral therapy is the treatment of choice. The large numbers probably reflect "the fact that more kids with ADHD are getting treatment than in the past," he said.
Thirteen percent of the diagnosed children aren't receiving any treatment, but Cuffe said "that's still pretty good. I think we're doing a better job of getting the kids who need it into treatment."
The survey also turned up notable differences among treatments in various states. Medication use ranged from 57 percent in California to 88 percent in Michigan. Rates of behavioral therapy were lowest in Tennessee, at 33 percent, and highest in Hawaii, at 61 percent.
Cuffe said the sizable differences may reflect the availability of behavioral treatment in some locations, but that more study is needed of cultural differences in various parts of the country.