Smoking too much marijuana increases the risk of broken bones

Regular cannabis smokers are more at risk of having a low-bone mineral density and of sustaining fractures, scientists have said. Later in life, this could put them at greater risk of developing osteoporosis, a condition in which the bones become brittle and fragile.

Cannabis has been legalised for therapeutic purposes in 25 US states, including four which have also authorised the recreational use of the drug. It has now also been well established that marijuana has therapeutic benefits as it potentially alleviates the symptoms of several health conditions, including chronic pain and anxiety.

But recreational consumption, poses a number of problems and some health risks have been identified by scientists. These include problems with blood vessel function, mental health problems, fertility problems, and an increased probability of developing periodontal disease.

In the latest study, published in The American Journal of Medicine, researchers suggest poor bone health could be another negative consequence associated with heavy use of cannabis.

Heavy use and bone density

The team, from the University of Edinburgh, recruited 170 adults who smoked cannabis regularly for recreational purposes, and 114 cigarette smokers who didn't consume cannabis.

Regular cannabis smokers were then divided into two group depending on the quantity they used. Heavy use was defined as having taken the drug on more than 5,000 occasions in a lifetime. In contrast, "moderate users" had smoked cannabis 1,000 times on average.

The scientists had the participants go through a specialised X-ray scan – a DEXA scan – to measure their mineral bone density. They found that bone density of people in the group of heavy cannabis users was about 5% lower than that of cigarette smokers who did not use cannabis.

They then measured their body mass index (BMI), and the results revealed it was also lower than in non-users of cannabis. Finally, the scientists discovered that fracture rate was also increased in heavy cannabis users throughout their life, compared with moderate cannabis smokers and non-users. This is an indicator of poor bone health, and on the long term, increased likelihood of developing osteoporosis as they advance in age.

Lead researcher Professor Stuart Ralston commented: "Our research has shown that heavy users of cannabis have quite a large reduction in bone density compared with non-users and there is a real concern that this may put them at increased risk of developing osteoporosis and fractures later in life."

Limits to this study include the fact that people self-reported their consumption habits. From one person to another, quantities smoked at one time may also vary so it is not always easy to make precise comparisons between participants.