Children Can Outgrow ADHD

Neuroscientists have known for a while that kids' brains are programmed to do the wave. The cortex, or outer layer of gray matter--which is responsible for such things as planning movement and suppressing inappropriate thoughts or actions--thickens from back to front during childhood and then thins out in adolescence, as unused neural connections go the way of football fans' empty beer cups. Thanks to nifty imaging techniques, the point at which the cortex reaches peak thickness is now recognized as an early milestone in brain maturation. But in a surprising new study, kids with attention-deficit/hyperactivity disorder (ADHD)--which affects 3% to 5% of school-age children--hit peak thickness in some regions an average of three years later than other kids. And the developmental lags are most pronounced in the part of the cortex that supports attention and planning.

The findings, published online this month in Proceedings of the National Academy of Sciences, may help explain why many children diagnosed with ADHD eventually grow out of it, as their brains slowly become more similar to those of their peers. The study will continue to track hundreds of adolescents to see if any of the ADHD kids ever fully catch up. More research is also needed to determine why half the kids with the disorder still have it as adults.

In the meantime, scientists caution that the news that children with ADHD appear to follow normal brain-development patterns, albeit a few years behind their peers, should not be taken as an O.K. to throw away their Ritalin. To the contrary, one of the study's co-authors, Dr. Judith Rapoport of the National Institute of Mental Health, says another study the team just submitted for publication (but which has yet to be peer-reviewed) suggests that in a few key areas of the brain that relate to attention and focus, kids with ADHD hew more closely to typical development trajectories only as long as they're on the stimulants. But when they go off their meds, she says, "they fall off the normal curve."