By Daniel DeNoon
WebMD Medical News
August 25, 2003 — People who keep taking drugs never seem to learn from their experience.
Now there’s an explanation. It offers insight into the bizarre behavior of drug addicts. But it also raises troubling questions about the long-term use of stimulants used to treat kids with attention deficit/hyperactivity disorder, ADHD.
Learning experiences literally change the brain, note Bryan Kolb, PhD, professor of psychology and neuroscience at the University of Lethbridge, Alberta, Canada, and colleagues. These changes in brain structure are thought to be how we learn from experience. It’s why we do things better — or know better than to do them — the second time around.
Drug users don’t seem to learn from experience. Even when it seems obvious that they’re ruining their health and destroying others’ lives, they persist in risky and irresponsible behavior. Why? To find out, Kolb and colleagues gave amphetamines and cocaine to lab rats.
After being moved to new cages filled with places to explore and interesting toys, the brains of normal rats grew lots of new connections. Rats given cocaine or amphetamines also explored and played in their new cages. But their brains didn’t grow new connections.
“We gave these drugs to the animals and put them in environments that should make big changes in their brains. But that didn’t happen. It was quite surprising,” Kolb tells WebMD. “It does lead to the idea that some of the stupid things addicts do — self-hurting behavior, risky acts — could be related to the fact that they are not learning the consequences of their behavior the way you and I should.”
Stimulant ADHD Drugs
Kids with ADHD have something in common with speed freaks. Both often take the same kinds of drugs — stimulants — day after day.
The rats in Kolb’s study took amphetamine. Different amphetamines — such as Adderall and Dexedrine — are effective ADHD treatments. Other stimulant drugs with similar effects include Ritalin, Concerta, Cylert, and Metadate.
These drugs aren’t the subject of Kolb’s report in the August 25 early edition of the Proceedings of the National Academy of Sciences. But Kolb’s ongoing work is looking at the effects of Ritalin.
“We’ve looked at Ritalin, although we haven’t done the same kinds of experiments as with amphetamine and cocaine,” Kolb says. “We do get changes in the brain with Ritalin. The child who is hyperactive may need changes to normalize the brain. But the other way to look at it is to say maybe it is harming these kids. We don’t really have an answer to this.”
Just because two drugs act a lot alike doesn’t mean that both drugs have the same effect on the brain, warns Alcino Silva, PhD, a professor at the UCLA Brain Research Institute. The way the brain changes in response to experience is very, very complex. Researchers are only beginning to understand them.
“Each of these drugs affects different memory systems — and some of these effects are very counterintuitive,” Silva tells WebMD. “It is difficult to say whether the findings with amphetamines and cocaine will be the same with Ritalin. These drugs don’t affect single systems. They affect a multitude of memory systems. So these effects may very well be specific to each person or each population.”
It’s exactly this complexity that Kolb worries about.
“Drugs that are stimulants — and other drugs as well — are not benign in their long-term effects,” he says. “There may be interactions with learning we need to worry about.
“There is a tendency for people to think that drugs like Ritalin aren’t a big deal. And if you have a kid who is tearing the house apart, you don’t want to abandon this drug if it’s the only thing that makes the kid’s life livable. But often it’s given because a parent or school has a low tolerance for disruptive behavior. Those are the situations where the ADHD drugs might be used too freely.”