Nearly one in five high school age boys in the United States and 11 percent of school-age children over all have received a medical diagnosis of attention deficit hyperactivity disorder, according to new data from the federal Centers for Disease Control and Prevention.

These rates reflect a marked rise over the last decade and could fuel growing concern among many doctors that the A.D.H.D. diagnosis and its medication are overused in American children.

The figures showed that an estimated 6.4 million children ages 4 through 17 had received an A.D.H.D. diagnosis at some point in their lives, a 16 percent increase since 2007 and a 53 percent rise in the past decade. About two-thirds of those with a current diagnosis receive prescriptions for stimulants like Ritalin or Adderall, which can drastically improve the lives of those with A.D.H.D. but can also lead to addiction, anxiety and occasionally psychosis.

“Those are astronomical numbers. I’m floored,” said Dr. William Graf, a pediatric neurologist in New Haven and a professor at the Yale School of Medicine. He added, “Mild symptoms are being diagnosed so readily, which goes well beyond the disorder and beyond the zone of ambiguity to pure enhancement of children who are otherwise healthy.”

And even more teenagers are likely to be prescribed medication in the near future because the American Psychiatric Association plans to change the definition of A.D.H.D. to allow more people to receive the diagnosis and treatment. A.D.H.D. is described by most experts as resulting from abnormal chemical levels in the brain that impair a person’s impulse control and attention skills.

While some doctors and patient advocates have welcomed rising diagnosis rates as evidence that the disorder is being better recognized and accepted, others said the new rates suggest that millions of children may be taking medication merely to calm behavior or to do better in school. Pills that are shared with or sold to classmates - diversion long tolerated in college settings and gaining traction in high-achieving high schools - are particularly dangerous, doctors say, because of their health risks when abused.

The findings were part of a broader C.D.C. study of children’s health issues, taken from February 2011 to June 2012. The agency interviewed more than 76,000 parents nationwide by both cellphone and landline and is currently compiling its reports. The New York Times obtained the raw data from the agency and compiled the results.

A.D.H.D. has historically been estimated to affect 3 to 7 percent of children. The disorder has no definitive test and is determined only by speaking extensively with patients, parents and teachers, and ruling out other possible causes - a subjective process that is often skipped under time constraints and pressure from parents. It is considered a chronic condition that is often carried into adulthood.

The C.D.C. director, Dr. Thomas R. Frieden, likened the rising rates of stimulant prescriptions among children to the overuse of pain medications and antibiotics in adults.

“We need to ensure balance,” Dr. Frieden said. “The right medications for A.D.H.D., given to the right people, can make a huge difference. Unfortunately, misuse appears to be growing at an alarming rate.”

Experts cited several factors in the rising rates. Some doctors are hastily viewing any complaints of inattention as full-blown A.D.H.D., they said, while pharmaceutical advertising emphasizes how medication can substantially improve a child’s life. Moreover, they said, some parents are pressuring doctors to help with their children’s troublesome behavior and slipping grades.

“There’s a tremendous push where if the kid’s behavior is thought to be quote-unquote abnormal - if they’re not sitting quietly at their desk - that’s pathological, instead of just childhood,” said Dr. Jerome Groopman, a professor of medicine at Harvard Medical School and the author of “How Doctors Think.”

Fifteen percent of school-age boys have received an A.D.H.D. diagnosis, the data showed; the rate for girls was 7 percent. Diagnoses among those of high-school age - 14 to 17 - were particularly high, 10 percent for girls and 19 percent for boys. About one in 10 high-school boys currently takes A.D.H.D. medication, the data showed.

Rates by state are less precise but vary widely. Southern states, like Arkansas, Kentucky, Louisiana, South Carolina and Tennessee, showed about 23 percent of school-age boys receiving an A.D.H.D. diagnosis. The rates in Colorado and Nevada were less than 10 percent.