A medical expert has said that healthy people should be allowed to take the controversial drug Ritalin, used to calm hyperactive children, to boost their own brain power.

Ritalinn also known as methylphenidate, is routinely used to treat children and young people with attention deficit hyperactivity disorder (ADHD), often characterised by inattention, hyperactivity and impulsiveness.

In addition, many healthy students are thought to use the drug, which enhances study skills and boosts attention focus, to improve their academic performance.

If not prescribed, Ritalin is a class B drug in the UK, meaning possession can lead to a five-year prison sentence and dealing could put you behind bars for 14 years.

However, bioethics expert Professor John Harris, of the University of Manchester, wrote in an article on bmj.com that if the drug was safe for children, adults should also be able to take it too.

"Safe always means safe enough and since no drugs are free of side effects, that always means the consumer has judged the risks of adverse effects worth taking, given the probable benefits," the BBC quoted Harris as saying.

However, Professor Anjan Chatterjee from the University of Pennsylvania said there are too many risks in taking Ritalin unless people are actually ill.

In the US, he said, the Food and Drug Administration labelled it with a "black box" - the most alarming of possible warnings - because of its high potential for abuse, dependence, risk of sudden death and serious adverse effects on the heart.