A new study has found that attention-deficit/hyperactivity disorder diagnoses are still on the rise in the U.S.

The study, published in the Journal of the American Academy of Child and Adolescent Psychiatry, found that 6.4 million American children had been diagnosed with ADHD as of 2011 to 2012. This represents a 42% increase (around 2 million more) from the number of children diagnosed with the condition as of 2003 to 2004. It also represents a full 11% of U.S. children aged 4 to 17.

“This finding suggests that there are a large number of young children who could benefit from the early initiation of behavioral therapy, which is recommended as the first-line treatment for preschool children with ADHD,” said Susanna Visser, lead author of the study and a researcher at the U.S. Centers for Disease Control and Prevention (CDC).

Along with these numbers, the study also found that medication rates for American children with ADHD are on the rise. Over half (3.5 million) of those children diagnosed with ADHD as of 2011 to 2012 were currently on medication for the condition, which can cause children to become impulsive and influence other behaviors. This represents a 28% increase from children medicated for the condition since just 2007 to 2008.

Overall, around 69% of children with ADHD as of last year were on medication for the disorder. Though medication was more common for children with more severe ADHD, the study found that 18% of U.S. children diagnosed with ADHD were neither being medicated nor receiving mental health counseling.

“This finding raises concerns about whether these children and their families are receiving needed services,” said Dr. Michael Lu, senior administrator for the Health Resources and Service Administration.