Ritalin Side Effects Rare in Long Run?

July 3, 2007 -- Ritalin, a drug used to treat attention deficit hyperactivity disorder ( ADHD), may not leave long-term side effects on the brain, a new study shows.

The Ritalin side effects study, published in The Journal of Neuroscience, was conducted on rats, not people.

The researchers included Teresa Milner, PhD, of the neurobiology division at New York's Weill Cornell Medical College.

ADHD is typically diagnosed in children, and Ritalin is one of the most commonly prescribed ADHD drugs, Milner's team notes.

The researchers injected young male rats with Ritalin for about a month, starting when they were 1 week old, to mimic Ritalin use in people, who take Ritalin by mouth.

The scientists split the rats into two groups. They examined the brains of one group of rats immediately after Ritalin treatment ended.

For comparison, the researchers checked the brains of the second group of rats three months after Ritalin treatment ended. By then, those rats were adults.

The rats also took two behavioral tests. In one test, the rats were placed in an open field and the researchers watched to see how quickly they scampered to find cover. In the other test, the rats had to navigate through a maze.

Ritalin Study's Results

The scientists noticed some subtle, short-term structural changes in the rats' brains immediately after Ritalin treatment ended. But those differences weren't major, and they faded within three months.

The Ritalin-related brain changes appear to "largely resolve with time," at least in rats, write the researchers.

As for the behavioral tests, the results were mixed.

In the maze test, the adult rats that had stopped Ritalin treatment three months earlier appeared to be less anxious than rats typically are. But that wasn't true in the other behavioral test, so the researchers didn't draw any firm conclusions about Ritalin's long-term side effects on normal anxiety.

The study focuses on the brain and behavioral side effects of Ritalin, not all possible side effects of the ADHD drug. It's not clear if the findings apply to people.