The head of Christian drug education charity Hope UK has called for a "long-term" approach to solve the problem of cannabis-related harm.

A study published at the end of last month revealed that marijuana users are 41 per cent more likely to suffer a psychotic illness such as schizophrenia later in life than those who never used the drug.

George Ruston, Director of Hope UK, said that the latest research simply added to mounting evidence from reports on cannabis and emerging true-life stories against cannabis that are putting "mounting pressure" on the Government to re-think its position on the drug and its current legal status.

Prime Minister Gordon Brown has already asked for a review of cannabis classification, which was downgraded to Class C from Class B a few years ago, and a consultation is underway to assess the Government's overall drug strategy.

But Mr Ruston said that the response to cannabis-related harm needed to further than a change in the law.

"Healthcare is needed as well for an increasing number of individuals, many of whom have conditions that have been made worse by cannabis use. But more attention needs to be paid to the less dramatic effects of cannabis which include apathy and short-term memory loss," he said.

"Research is needed to show just how much potential is lost because regular cannabis use results in lower examination results and an inability to fulfil potential.

"A long-term approach needs to be taken which includes education and prevention."