The study has the potential to quiet some of the controversy surrounding ADHD, both as a diagnosis and for the way it is treated. There are camps of experts and parents who believe an ADHD diagnosis is simply a label for a child who is lazy, unmotivated or developing slowly.
Others are not convinced that medication is the proper treatment for people with ADHD, suggesting behavioral therapy and tutoring as alternatives.
A federal study from the 1990s called the Multimodal Treatment Study of Children with ADHD (MTA) generated controversy earlier this year when some suggested that the results showed that treating ADHD with medication had almost no beneficial effects over eight years.
"There is a resistance to medicating your child," said Richard Scheffler, professor of health economics and public policy at UC Berkeley's School of Public Health and another author on the study. "And some think you need to get the old ruler out."
In fact, the MTA study showed that, during 14 months of controlled trials with ADHD medications, talk therapy and routine medical care, those who received drugs showed fewer symptoms of ADHD than their peers. Data collected during follow up studies showed tapering in the beneficial effects of ADHD medication because the patients were released from the confines of a controlled trial into community care where there was less oversight.
"Absence of evidence is not evidence of absence," said L. Eugene Arnold, professor emeritus of psychiatry at Ohio State University and one of the authors of the MTA study. "To deny that there is a problem does not seem to be the sensible approach."
And the MTA study proved this principle. In one group of same-sex children, all in the same school and classroom, those with ADHD showed decreased symptoms in a follow up study eight years later, but they were still not as advanced as their peers, both behaviorally and academically.
By contrast, Hinshaw said that children with ADHD gained about one fifth of a school year almost immediately after starting medication. The children gained even more in reading skills -- about a third of a school year -- but those skills took a year longer to acquire because they are more complicated and require practice.
"The one thing that works for attention deficit is medicine, like it or not," said Dr. Gary Trock, director of Pediatric Neurology at Beaumont Hospital in Royal Oak, Mich. But Trock added that for most, a combination of behavioral therapy or tutoring and other one-on-one assistance produced the best outcomes.
Though it is difficult to compare the results of a controlled study to one that pulls data from the natural population, Arnold said that the Berkeley study findings were even more unusual because of where the data came from.
In the general population, a child receiving treatment for ADHD is likely in worse condition than someone who does not need treatment or needs less aggressive treatment.
"The fact that [these kids] made gains over kids who didn't get medications is interesting," Hinshaw said.
The researchers did admit potential problems with their data set because they could not control the parameters for who took medication for ADHD and how.
For example, people who were being treated for ADHD may have had more motivated parents.