Marijuana may cause gum disease

Heavy cannabis smoking has been identified as a major cause of gum disease in a study involving researchers from the University of Otago, King's College in London, Duke University and the University of North Carolina in the USA.

Using data gathered through the Dunedin Multidisciplinary Health and Development Study (DMHDS), which tracks a group of 1000 people born in Dunedin in 1972-73, they found heavy cannabis smoking was responsible for more than one-third of the new cases of gum disease by age 32.

Their findings have been published in the prestigious Journal of the American Medical Association.

Professor Murray Thomson from the University of Otago School of Dentistry says periodontal disease, or gum disease, is one of the most common diseases of adulthood and causes a range of problems, including the loss of support for the teeth.

"There is also an emerging body of evidence that it may also be a risk factor for heart disease, stroke and even pre-term birth," says Professor Thomson.

Cigarette smoking has been a long-established risk factor for gum disease but this is the first study looking at cannabis.

"The problem is not the smoke itself - it's what's in the smoke," he says.

"In the mouth, there is a fine balance between tissue destruction and tissue healing and the various toxins in cannabis smoke disrupt that."

Professor Thomson says their findings have added strength because rather than using a single cross-sectional survey, they used a longitudinal study in which the state of participants' gums and their use of cannabis and tobacco were tracked over many years.

For the study, they identified heavy cannabis users as those in the top 20% of cannabis use, equivalent to an average of 41 or more occasions per year between ages 18 and 32.

Professor Thomson says they had to be mindful that cannabis smokers are also much more likely to be cigarette smokers.

"But even after allowing for this, we found heavy cannabis smokers had three times the risk of having established gum disease by age 32," he says.

"When we looked at just those who had never smoked tobacco, the relationship between cannabis and gum disease was even stronger.

"We have been able to calculate that over one-third of new cases of gum disease between the ages of 26 and 32 could be put down to cannabis use."

Professor Thomson says the findings account for some of the unexplained variation in gum disease among younger adults.

(Source: Journal of the American Medical Association: University of Otago: February 2008)