Cannabis can help to prevent osteoporosis in the elderly, according to research. The findings could lead to new treatments being developed to treat the crippling condition.

Researchers at University Edinburgh also found, though, that the drug can weaken the bones of younger people.

The discovery was described as “exciting” by charities, but they cautioned that it was important to understand the negative consequences of cannabis use on young bones.

It was previously recognised that bone development was affected when a molecule in the body, known as the cannabinoid receptor type 1, came into contact with cannabis. It was not clear, though, whether the impact was good or bad. Now the Edinburgh team has established that this depends on the age of the user.

They exposed mice to compounds similar to those found in cannabis. They found that, in the young mice with the receptor, the compounds increased the rate at which bone tissue was destroyed.

When the older mice with the receptor were exposed to the same compounds, though, their bone loss decreased and the accumulation of fat in the bones was prevented. Among older people bone regeneration normally slows down and fat builds up, causing osteoporosis.

Stuart Ralston, Professor of Rheumatology at the university, who led the study, said: “This is an exciting step forward, but we must recognise that these are early results. We plan to conduct further trials soon and hope the results will help to deliver new treatments that will be of value in the fight against osteoporosis.”

Professor Ralston said that the ideal way forward would be to develop a drug which was similar to cannabis but which did not have the same psychotropic effects. He added that smoking cannabis with tobacco was bad for bones at any age.

It is estimated that three million people have osteoporosis in Britain. One in two women and one in five men over the age of 50 will suffer broken bones because of the condition.

Claire Bowring, medical policy officer for the National Osteoporosis Society, said: “This is an exciting study ... but it is important to understand the potential negative effects on peak bone mass [in the young] as well as the positive protection from age-related bone loss. We look forward to further research to see if these effects are mirrored in [people].”