"ADHD is becoming a more common diagnosis in early childhood, so understanding how the disorder progresses in this age group is critical," lead investigator Dr. Mark Riddle, a pediatric psychiatrist at the Johns Hopkins Children's Center, said in a statement. "We found that ADHD in preschoolers is a chronic and rather persistent condition, one that requires better long-term behavioral and pharmacological treatments than we currently have."
The study found that nearly 90 percent of the 186 preschoolers the researchers followed continued to struggle with ADHD symptoms six years after diagnosis.
Children taking ADHD medication had just as severe symptoms as those who were medication-free, the study found.
More than 7 percent of U.S. children are treated for ADHD, the investigators say.
Other institutions involved in the research were Columbia University Medical Center, Duke University, the Nathan Kline Institute, University of California-Irvine and University of California-Los Angeles.
The research was funded by the National Institute of Mental Health