CHICAGO -- Regular use of marijuana in young adulthood is associated with periodontal disease, according to a study in Wednesday's issue of the Journal of the American Medicine Association.

Periodontal disease is one of the most common chronic diseases in adults, with inflammation that can extend deep into the dental tissues, causing loss of supporting connective tissue and possible loss of teeth. Tobacco smoking is recognized as the primary behavioral risk factor for the condition, and it is thought cannabis smoking may have a similar effect, according to background information in the article.

JAMA reported that W. Murray Thomson, Ph.D., of the Dunedin School of Medicine, Dunedin, New Zealand, and colleagues conducted a study to determine whether cannabis smoking is a risk factor for periodontal disease.

The study included 903 participants who were born in Dunedin in 1972 and 1973 and assessed periodically: cannabis use was determined at ages 18, 21, 26, and 32 years and dental examinations were conducted at ages 26 and 32 years. The most recent data collection (at age 32 years) was completed in June 2005.

Three cannabis exposure groups were determined: no exposure (293 individuals), some exposure (428), and high exposure (182). Some exposure was defined as an average of one to 40 occasions of cannabis use reported during the years assessed; high exposure as an average of 41 or more occasions of cannabis use during those years. At age 32 years, 265 participants had one or more sites with 4 mm or greater new attachment loss of gum tissue, and 111 participants had one or more sites with 5 mm or greater. New attachment tissue loss between the ages of 26 and 32 years in the none, some, and high cannabis exposure groups was 6.5 percent, 11.2 percent, and 23.6 percent, respectively.

After controlling for tobacco smoking (measured in pack-years), sex, irregular use of dental services and dental plaque, compared with those who had never smoked cannabis, those in the highest cannabis exposure group had a 60 percent increased risk for having one or more sites with 4 mm or greater new attachment tissue loss; a 3.1 times greater risk for having one or more sites with 5 mm or greater new attachment tissue loss; and a 2.2 times increased risk for having new attachment tissue loss.

Tobacco smoking was strongly associated with periodontal disease, but there was no interaction between cannabis use and tobacco smoking in predicting the condition's occurrence.

"The study's demonstration of a strong association between cannabis use and periodontitis experience by age 32 years indicates that long-term smoking of cannabis is detrimental to the periodontal tissues and that public health measures to reduce the prevalence of cannabis smoking may have periodontal benefits for the population," the authors wrote in JAMA.

"Although definitively establishing the periodontal effects of exposure to cannabis smoke should await confirmation in other populations and settings, health promoters and dental and medical practitioners should take steps to raise awareness of the strong probability that regular cannabis users may be doing damage to the tissues that support their teeth," they added.