Controversial drug Ritalin has had startling effects on hyperactive children but could it have uses for adults too? Claire Sanders reports on how it can benefit short-term recall.
Researchers have demonstrated for the first time that Ritalin, the controversial drug commonly prescribed to children with Attention Deficit Hyperactivity Disorder (ADHD), can improve mental performance in "normal" adults.
Mitul Mehta, who carried out the research with Barbara Sahakian at the department of psychiatry at the University of Cambridge, says: "Our findings open up an exciting prospect for the ability to pharmacologically target brain functions that you wish to improve - in those with and without brain dysfunction.
"The results indicate that Ritalin can improve short-term memory, even in those individuals without memory problems. However, this drug is a controlled substance in the United Kingdom, in the same class as cocaine, so we wouldn't advise people to start taking it in the hope it may improve, for example, their exam performance," he says.
ADHD affects 3-5 per cent of children. In the United States, more than 2 million children take Ritalin. United Kingdom prescriptions of the drug have risen more than 36-fold between 1993 and 1998, from 3,500 to 126,500.
Mehta says: "It has been found that children with ADHD benefit greatly from Ritalin treatment in terms of their behaviour and other brain functions, such as attention and memory. It is the closest thing we have to a magic pill. However, we don't know exactly how the drug works."
In an attempt to find out more, the researchers asked ten adults, who did not suffer from ADHD, to carry out a task that would require them to use their "working memory". "This is the memory you use to hold information in when you want to use it for a particular task," says Mehta. "For example, remembering a phone number you've looked up until you dial it."
The Cambridge researchers used a memory task presented on a touchscreen computer. The volunteers were shown 12 red boxes on the screen.
They had to search through the boxes, one by one, looking for hidden tokens. They had to remember where they had previously found tokens as they were not allowed to return to those boxes.
Each volunteer carried out the task twice, with Ritalin being administered only half of the time. While the volunteers carried out the task their brains were scanned using a positron emission tomography scanner.
The scanner showed increased blood flow to the frontal and parietal lobes of the brain. For those on Ritalin, blood flow in the same areas was changed. "This result is important, because these parts of the brain are known to be particularly impaired in those with ADHD," says Mehta.
What was striking was that the drug made the volunteers much better at the memory test. While those not on Ritalin made an average of 16 errors on each problem in the exercise, those on Ritalin made just 11 errors.
Ritalin is controversial because it is a stimulant drug, related to amphetamine and cocaine. "Its effect appears to be paradoxical," says Mehta, "because it is a stimulant that calms children down".
It is now believed that Ritalin acts to increase the synaptic concentration of dopamine by blocking its re-uptake. This means that Ritalin stimulates the chemical dopamine, keeping it in the brain longer. "Dopamine is one of the chemicals in the brain that is heavily implicated in the pathology of numerous brain disorders," says Mehta.
"Correct levels of dopamine are important for basic everyday functions such as attention and memory. There is a wealth of animal research on the dopamine system, but we are yet to fully understand it in humans."
Ritalin has come into widespread use -ahead of a proper understanding of how it works - partly because it was discovered by accident. In the 1930s, a doctor called Charles Bradley was working with children with pulmonary conditions. He administered a drug similar to Ritalin and found that in those children who had also shown behavioural problems there was a marked improvement in behaviour. In the late 1950s, the drug was developed and Ritalin was first prescribed in the 1960s.
Last year, Richard DeGrandpre, visiting professor of psychology at St Michael's College in Vermont, in the United States, published a book called Ritalin Nation. In it he argued that the US, where the practice of prescribing Ritalin accounts for 80 per cent of the drug's consumption worldwide, has developed a "rapid-fire" culture that has "transformed human consciousness". He said that the American "culture of speed" had "created a nation hooked on speed and the stimulant drugs that simulate speed's mind-altering effects". He said that Ritalin was not the answer to ADHD.
The increased use of Ritalin in the UK has also been criticised by the United Nations' drug control board. In May of this year, a pressure group, Stimulants are not the Answer, was founded in the United Kingdom to support non-drug treatments for the condition.
However, the drug has strong supporters, with many parents describing it as a "miracle" drug. Mehta says: "For some children Ritalin has changed their lives and it is very moving to talk to them. They talk of, at last, being able to be themselves, once they take Ritalin. There may be some value in non-drug treatments, but the use of Ritalin cannot be dismissed in the light of all the evidence."
He says that research shows the risks of not prescribing Ritalin are higher than those of prescribing it. "Children on Ritalin have a period of calm, enabling them to develop better relationships with their mothers. There is also evidence that those with ADHD not on Ritalin have a greater chance of going on to abuse drugs in some way."
The symptoms of ADHD in a half to a third of children do recede with age. There is as yet no clear evidence that Ritalin alters this change, says Mehta.
Mitul Mehta, whose research is funded by the Medical Research Council and the Wellcome Trust, has since moved to Imperial College, London, where he plans to continue his ADHD research.