ADHD drugs may boost arousal more than attention : Shots

Scientists are updating their view of how drugs like Adderall and Ritalin help children with attention deficit hyperactivity disorder stay on task.

The latest evidence comes from a study of thousands of adolescent brain scans that confirms earlier hints that stimulant drugs have little effect on the brain networks that control attention.

Instead, scientists say drugs activate networks involved in vigilance and anticipation of pleasure. report in the magazine Cell.

“We think it's the combination of arousal and reward, sort of a one-two punch, that really helps kids with ADHD when they take this medication,” says Dr. Benjamin Kaya pediatric neurologist at Washington University School of Medicine in St. Louis and lead author of the study.

The results, along with those from smaller studies, support “a shift in thinking about how stimulants work in people,” says Peter Manza, a neuroscientist at the University of Maryland who was not involved in the study.

A new study analyzed the data Study of cognitive development of the adolescent braina federally funded program involving brain scans of nearly 12,000 children. About 4% of these children had ADHD at the time of their participation in the study, and nearly half of them were taking prescription stimulants.

ABOUT 3.5 million children ADHD medications are being taken in the US, and the numbers are growing.

Medicines and brain networks

The brain scan data included a type of MRI that measures brain activity when a person is at rest. This allowed Kay and the team to see which areas of the brain became more active in response to the drugs.

Kay expected to find a lot of activity in those areas that allow a person to control what he pays attention to.

“I actually found that these were the parts of the brain that were least affected,” he says.

Instead, the drugs stimulated areas that help people stay awake and alert, as well as areas that anticipate pleasurable rewards.

This dual effect appears to occur because stimulants such as Ritalin and Adderall increase levels of two different chemicals in the brain, said Dr. Nico Dosenbach, senior author of the paper and a professor at the University of Washington.

The first chemical is norepinephrine, which prepares the body and brain for action.

The study found that this fight-or-flight response counteracts the usual cognitive decline associated with sleep deprivation and affects cognitive function. Lack of sleep is a problem for many teenagers, especially those with ADHD.

The second brain chemical is dopamine, which plays an important role in the brain's reward system. And boosting dopamine levels may help children with ADHD feel more positively about everyday tasks such as homework.

Usually the brain expects: “This is going to be terrible, this is going to be boring,” says Dosenbach. “Dopamine can make you more tolerant because you feel a small, low-level reward.”

It's too early to tell what's happening, Manza said. But he agrees that stimulants have an effect on the brain that helps children with ADHD do things like homework.

“They don't find math problems very interesting, but after a dose of Ritalin they may find them more interesting,” he says, “and so they are willing to persist and finish the problem.”

Brain scan before taking drugs?

The new study's findings shouldn't undermine doctors' confidence in the effectiveness of stimulants for ADHD, Kay says. But they suggest it is important to rule out factors such as sleep deprivation before turning to medication.

“This was a really personal article for me because I prescribe these medications all the time,” Kay says.

The results also suggest that brain scans may ultimately provide insight into whether a child would benefit from drug treatment, Manza said.

“Stimulants don't work for everyone,” he says, “so we need to do a better job of targeting the people who need them.”

According to Manza, one day MRI will be the best way to diagnose ADHD. He says this is vital in an era when more children and young people are being told they have a disorder and should take medication.