How Ritalin Works in ADHD

From the WebMD Archives

July 12, 2001 -- Every day millions of U.S. kids get a dose of Ritalin. It's been known for years that the drug improves symptoms of attention deficit hyperactivity disorder, or ADHD. Now researchers know why the drug works.

The findings, reported this year in scientific journals, were featured this week in a press conference at New York's Brookhaven National Laboratory. Part of the U.S. Department of Energy, the lab is filled with high-tech imaging devices that can peer into the human brain.

A research team led by Nora Volkow, MD, head of Brookhaven's biology and medical departments, finds that the brains of children with ADHD have too little dopamine, a brain chemical needed for several vital brain functions. Why? It's because the children's brains have too many molecules that suck up dopamine before it does its thing. Ritalin gums up these molecules, so they leave the dopamine alone.

"Dopamine is not only involved with movement and attention but with reward and motivation -- it modulates brain signals that say, 'This is important! Pay attention!'" Volkow says. "So we think Ritalin highlights the task the child is doing. If you are bored, I cannot get your attention. But if you are interested, I can. Ritalin is in this way improving the performance of the child."

When a person concentrates on a task, the part of the brain that is working becomes highly active. But other parts of the brain are active, too. This "white noise" helps a normal person make new, creative associations, Volkow says. But for someone with ADHD, the white noise drowns out the main signal. The new findings show that by increasing dopamine to more normal levels, Ritalin amplifies the main program.

"The more we understand [about how Ritalin works] the more confidence we have that the treatment is appropriate," says James M. Swanson, PhD, director of the Child Development Center at the University of California, Irvine. "It is never an easy thing for parent to put a child on medication. This will help that decision process."

Swanson, who works exclusively with ADHD children, is no knee-jerk proponent of Ritalin, also known as methylphenidate. He suggests the drug be reserved only for children who do not sufficiently improve after intensive efforts fail to modify their behavior.

Ritalin is not considered to be a highly addictive drug. But drugs that are highly addictive -- cocaine, for example -- also increase dopamine levels in the brain. Volkow notes that the long-term consequences of Ritalin use remain unknown.

"We have seen that cocaine makes profound changes in blood flow to the brain, so is this the same for Ritalin? Could [long-term] use of Ritalin affect the brain to make it more vulnerable to drug addiction?" Volkow asks.

"It is a key question that nobody has answered. We get mixed findings from studies of ADHD children treated with and without Ritalin," she says. "One study shows if you don't treat them with Ritalin you see more drug use in later life, and another study shows exactly the opposite. At the doses you give it to children, no studies have been done."

Volkow notes, however, that unchecked ADHD itself can be very harmful to a child's development.

"Even if Ritalin does affect brain function, what are the consequences if you don't treat?" she asks. "We need to understand them so we can learn to prescribe these drugs better. Right now there are only questions, no answers."