Scientists have made a finding they hope will lead to new drugs to treat osteoporosis and other bone diseases.
Osteoporosis increases the risk of bone fractures
They have discovered that blocking the action of cannabis-like substances produced naturally by the body can reduce bone loss.
The findings also suggest that using cannabis might have a damaging effect on the health of bones.
The research, led by the University of Aberdeen, is published in the journal Nature Medicine.
It focused on the effects on the bones of chemicals called endogenous cannabinoids.
These substances act in the same way that cannabis does, by attaching themselves to receptors in our body which then play a part in a number of the body's processes, including controlling our appetite.
The latest study has shown these receptors are also present in bone cells - and play a crucial role in regulating bone density and the turnover of bone tissue.
Preventing bone loss
The researchers also discovered that drugs which block the cannabinoid receptors proved highly effective in preventing bone loss.
Lead researcher Professor Stuart Ralston, now at the University of Edinburgh, said: "This is an important finding since it demonstrates that the receptors which cannabis acts upon are not only important in the nervous system, but also in the control of bone metabolism.
"The fact that compounds which blocked cannabinoid receptors are highly effective at preventing bone loss is particularly exciting, since it shows that these drugs could provide us with a completely new approach to the treatment of osteoporosis and other bone diseases."
Dr Ruth Ross, a cannabinoid research scientist at the University of Aberdeen, added: "Cannabinoid receptor blockers have recently been shown to be safe and effective for the treatment of obesity.
"The fact that they may also be potent inhibitors of bone loss has major therapeutic implications."
The researchers also discovered that 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.
More than 250,000 people in Britain suffer osteoporosis-related fractures each year, with related health care costs of over £1,700m.
However, the most widely used of drug treatments for osteoporosis, cancer-related bone diseases, rheumatoid arthritis and other bone diseases are inconvenient to take and can be associated with various undesirable side effects.
Professor Ralston said: "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."
A spokesman for the National Osteoporosis Society said: "It is very encouraging from our point of view that new areas are being explored in osteoporosis research and funding is being made available to carry out this vital work.
"This area of study is still at the very early stages, but it is always interesting to hear about these pieces of research and we will watch with interest to see what happens."
The research was funded by the Arthritis Research Campaign.