Smoking large amounts of cannabis over a long period of time could lead to reduced bone density and a higher risk of fractures according to new UK research.
Carried out by the University of Edinburgh, UK, the study is the first to look at bone health amongst cannabis users.
For their research the team recruited 170 people who smoked cannabis regularly for recreational purposes and 114 who didn't use the drug at all.
The researchers defined heavy users as those who reported smoking cannabis on 5000 or more occasions in their lifetime, although in the study the average heavy cannabis user had taken the drug more than 47,000 times.
Those who had taken the drug about 1000 times were described as moderate users.
Whether heavy, moderate or non-users, all participants had their bone density measured using a specialized x-ray technique called a DEXA scan.
The results showed that the bone density of heavy cannabis users was about 5 percent lower than cigarette smokers who did not use cannabis, which the researchers say could put heavy users at an increased risk of developing osteoporosis later in life. The researchers also found that when compared to non-users, heavy users also experienced more fractures, however no difference was found between moderate users and non-users.
Perhaps surprisingly, as cannabis is known to increase appetite, the study also found that the heavy users had a lower body weight and a reduced body mass index (BMI), with the researchers suggesting that large amounts of the drug over a long period of time may actually reduce and not increase the appetite. That finding is also bad news for bone health, and could be one of the contributing factors to the lower bone density seen in this group of users.
Lead researcher Professor Stuart Ralston commented on the results saying, "We have known for a while that the components of cannabis can affect bone cell function but we had no idea up until now of what this might mean to people who use cannabis on a regular basis."
However the team did add that further research is needed to better understand the link between cannabis use and its negative effect on bone density.
The study, which was funded by Arthritis Research UK, is published in the American Journal of Medicine.