Cannabis linked to bone disease

EXCESSIVE use of cannabis might lead to brittle bone disease, new research has shown.

Scottish scientists found that the drug can cause increased bone loss, which in turn leads to osteoporosis. The findings add to a growing body of evidence on the dangers of cannabis and prompted campaigners to renew their calls for the government to rethink its drugs law.

Researchers at Aberdeen University made the discovery while carrying out a study, which was funded by the Arthritis Research Campaign, into chemicals produced naturally in the body called endogenous cannabinoids. The good news is that through understanding for the first time that cannabinoids regulate bone density, scientists have paved the way for new drugs to treat bone disorders.

But the study, published in the journal Nature Medicine, also sounded a warning for the 3.5 million cannabis users in the UK. Professor Stuart Ralston, who led the study, said: "I wouldn't want to strike fear into everyone who uses the drug, but our tests lead us to the conclusion that it might cause bone loss."

Cannabinoids act in the same way as chemicals in cannabis by attaching themselves to receptors in the body, stimulating appetite or bone metabolism. Prof Ralston said: "These experiments were not carried out on human patients, but the prediction is that if someone is continually exposed to cannabis, then it would stimulate the cells that would cause a loss of bone. The drugs which stimulate these receptors - and mimic the effects of cannabis - were detrimental to bone and caused increased bone loss, which could, in turn lead to osteoporosis."

Prof Ralston, now based at Edinburgh University, said the discovery opened the door to drugs used to treat obesity being used to prevent and treat osteoporosis. He said the drugs that block cannabinoid receptors to suppress appetite could also be used to stop bone loss.

He explained: "We were looking at the role of these cannabinoid receptors - the molecules that, like cannabis, would bind on to the bone.

"We started using drugs that would block these receptors and we found that they completely prevented bone loss. It was a very, very impressive effect."

More than 250,000 people in Britain suffer osteoporosis-related fractures each year, but Prof Ralston said that the most widely used drug treatments for osteoporosis, cancer-related bone diseases, rheumatoid arthritis and other bone diseases were inconvenient to take and can be associated with various undesirable side-effects.

He added: "There is a real need to identify new drugs that can inhibit bone loss, and it looks like blockers of cannabinoid receptors may fit the bill as a new class of drugs for the treatment of bone disease."

Prof Ralston is now leading further research into the effects of cannabis on bone disease.

This month Jeanie Rae, of Stirlingshire, who has breast cancer, was the first person in Scotland to be prescribed a purified version of cannabis for medical reasons.

But campaigners said the recent findings add to the increasing evidence showing the dangers of the drug. Alistair Ramsay, the director of Scotland Against Drugs, said cannabis on the street is no longer a "soft, decent" drug.

He said: "There is gathering evidence of a growing range of conditions caused by cannabis. Emphysema and early onset of lung cancer are now joined by possible osteoporosis and mental illness.

"Clearly, this is a drug for which, although under very controlled circumstances by a GP may have some benefit, the uncontrolled unsupervised use carries many dangers."

Cannabis was reduced from a Class B to Class C drug last year, but Charles Clarke, the Home Secretary, has asked the government's advisory council on drugs to consider reversing the classification following evidence linking the drug to mental illness.

The drug has been linked to a number of criminal cases, including the Jodi Jones trial - where schoolboy murderer Luke Mitchell was shown to have smoked cannabis.

Mr Ramsay said drug laws in the UK need to be revisited in the light of new research on the dangers of the prolonged use of drugs like cannabis and ecstasy.

He added: "The time has come to have a long, hard look at drug law in the UK influenced directly by a range of experts, from international treaties right through to the latest research."

However, Don Barnard, of the Legalise Cannabis Alliance, was sceptical of the new findings, saying: "Research on cannabis is usually orchestrated to show the government's point of view."

But he welcomed further research. "That's the only way we are going to get rid of a law which leads to people being jailed for using and growing cannabis."