During the 14-month controlled treatment period, children with ADHD were assigned to receive usual community care or one of three treatments: medication alone, medication plus behavioral therapy, or behavioral therapy only.

Ratings from both family members and teachers favored the combination treatment, and careful medication management was more successful than medication provided through usual community care sources.

After 14 months of controlled treatments, families were free to choose the kind of treatment their children received, if any.

In one of the follow-up studies, researchers evaluated the children three years after the controlled treatment ended -- when they were 10 to 13 years old. They found that while 45 percent to 71 percent of the children were taking medication, continuing medication treatment was no longer associated with better outcomes.

"Our results suggest that medication can make a long-term difference for some children if it's continued with optimal intensity and not started or added too late in a child's clinical course," Peter Jensen, a researcher at Columbia University, said in a prepared statement.

A second study in the same issue of the journal found that children differed in their response to medication. A team at the University of California, Irvine, reported that about a third of the children showed a gradual, moderate improvement; about half showed a large initial improvement that was sustained through the third year of follow-up; and about 14 percent responded well initially but then symptoms returned during the second and third years.

The study's authors suggested that withdrawing the medication on a trial basis may help physicians determine if some children still need to take medications.

Another study by the same group suggested that taking medication for ADHD was associated with slowed growth. A group of 65 children who had never taken medication grew larger -- about three-quarters of an inch taller and six pounds heavier -- than a comparison group of 88 children who stayed on medication over the three years of follow-up.

A final article from the University of Pittsburgh reported that, despite treatment, children with ADHD showed higher-than-normal rates of delinquency than kids without ADHD (27.1 percent vs. 7.4 percent) and higher rates of substance abuse (17.4 percent vs. 7.8 percent) after three years.

Researchers will continue to follow the children to determine their outcomes in adolescence and adulthood.

More information

The U.S. Centers for Disease Control and Prevention has more about ADHD.